tag:theconversation.com,2011:/us/topics/echolocation-30861/articlesEcholocation – The Conversation2024-03-04T16:54:22Ztag:theconversation.com,2011:article/2248842024-03-04T16:54:22Z2024-03-04T16:54:22ZDiscovering the world of dolphins and their three ‘super senses’<figure><img src="https://images.theconversation.com/files/579179/original/file-20240129-15-onehyv.jpg?ixlib=rb-1.1.0&rect=0%2C12%2C4265%2C2826&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Dolphins can communicate very effectively.</span> <span class="attribution"><a class="source" href="https://unsplash.com/fr/photos/photographie-en-accelere-de-deux-dauphins-nageant-dans-la-mer-ZYPQDN_xSqk">Arielle Allouche/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Imagine that you’re in a comfortable room with your cat. You’re both sharing the same space, temperature and lighting. But while you’re enjoying the décor, and perhaps a book or the taste of hot chocolate, the cat seems intrigued by something else. Maybe she’s looking for a treat or making sure that no one infringes on “her” preferred spot, a comfortable armchair near the heater.</p>
<p>All this is to say that even if you and your pet are in the same place, you both perceive your environment differently. In 1934, the German scientist Jakob von Uexküll defined it as the “umwelt” (<em>environment</em> in German). The <em>umwelt</em> is each individual’s <a href="https://monoskop.org/images/1/1d/Uexkuell_Jakob_von_A_Stroll_Through_the_Worlds_of_Animals_and_Men_A_Picture_Book_of_Invisible_Worlds.pdf">perception of the world in which he or she lives</a>.</p>
<p>But how do other animals perceive the world around them? I’m particularly interested in those that live in habitats that are drastically different from those of humans, such as dolphins in the vastness of the ocean.</p>
<p>By understanding animals’ perceptions, we can better protect them. In the case of dolphins, knowing how they perceive their environment means knowing the impact of underwater noise on their communication and taking measures to control it in protected marine areas.</p>
<p>So let’s dive in and discover the three super-senses of dolphins: magnetic perception, electrical perception and echolocation.</p>
<h2>Magnetic perception</h2>
<p>Magnetic perception was first demonstrated in dolphins in 1981: American researchers found <a href="http://www.ncbi.nlm.nih.gov/pubmed/7256282">fragments of magnetite closely linked to neuronal connections</a> extracted from the brains of four stranded common dolphins. Surprised by the discovery, the scientists suggested that it could have a sensory function or play a role in navigation.</p>
<p>In 1985, another team of researchers discovered a <a href="https://journals.biologists.com/jeb/article/120/1/1/4953/Evidence-From-Strandings-for-Geomagnetic">relationship between cetacean stranding positions and the Earth’s geomagnetic field</a>: several species of whales and dolphins actually tend to strand in places where the magnetic intensity is low. If cetaceans use the Earth’s magnetic field to find their bearings, one hypothesis is that areas where the magnetic intensity is weaker would increase the likelihood of stranding due to a lack of bearings.</p>
<p>In 2014, with a team of scientists from the University of Rennes 1, I carried out a behavioural study that enabled us to show that <a href="https://hal.science/hal-01134557">bottlenose dolphins have a magnetic sense</a>. We tested the spontaneous response of six captive dolphins to the presentation of two objects with the same shape and density: the first contained a block of magnetically charged neodymium (a metal), while the second device was completely demagnetised.</p>
<p>The dolphins approached the device much more quickly when it contained a block of strongly magnetised neodymium. This allowed us to conclude that the dolphins are able to discriminate between the two stimuli on the basis of their magnetic properties.</p>
<p>These data support the hypothesis that cetaceans can determine their location using the Earth’s magnetic field and that, consequently, when this field is weaker, the tendency to strand is greater.</p>
<h2>Electrical perception</h2>
<p>When fish move their muscles and skeletons, they emit weak electric fields. Some marine predators, particularly in benthic areas (at the bottom of the ocean) – where visibility is reduced, are able to perceive their prey via these electric fields. A range of aquatic and semi-aquatic species share this ability.</p>
<p>In dolphins, electroreception was demonstrated for the first time in 2012. The structures known as hairless <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2011.1127">vibrissal crypts</a> on the rostrum of Guiana dolphins (one of the smallest species) serve as electroreceptors. In the study, the researchers noted that the vibrissal crypts have a well-innervated ampullary structure, reminiscent of the ampullary electro-receptors in other species such as <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/elasmobranch">elasmobranchs</a> (sharks and rays), lampreys, paddlefish, catfish, certain amphibians and even in the platypus and echidna). These vibrissal crypts are thought to function as sensory receptors capable of picking up small electric fields emitted by prey in aquatic environments.</p>
<p>The same study also found behavioural evidence of electroperception. A male Guiana dolphin was trained to respond to electrical stimuli of the order of magnitude of those generated by small-to medium-sized fish. For example, a goldfish 5 to 6 centimetres long produces electric fields of 90 microvolts per centimetre, with a peak energy at 3 hertz. Bioelectric fields of 1,000 microvolts per centimetre have been reported in flounders – a magnitude equivalent to 1/100,000 of the electric current of a light bulb.</p>
<p>The dolphin was trained to place its head in a hoop and touch a target with the tip of its rostrum. It had to leave the hoop when a stimulus was presented, and when no stimulus was presented, it had to remain in the hoop for at least 12 seconds.</p>
<p>This experiment showed that dolphins perceive weak electric fields – a sensitivity comparable to that of platypus electroreceptors. The first clear demonstration of electroreception in platypuses was carried out in Canberra in 1985 by a German-Australian team, which showed that <a href="https://www.nature.com/articles/319401a0">they sought out and attacked submerged and otherwise invisible batteries</a>. In 2023, a team of researchers found similar <a href="https://pubmed.ncbi.nlm.nih.gov/38035544/">detection thresholds in bottlenose dolphins</a>, using the same behavioural test.</p>
<p>It is now thought that electroreception can facilitate the detection of prey at close range and the targeted killing of prey on the seabed.</p>
<p>In addition, the ability to detect weak electric fields could enable dolphins to perceive the Earth’s magnetic field by means of magnetoreception, which could enable them to orientate themselves on a large scale.</p>
<h2>Echolocation</h2>
<p>The most studied sense in dolphins remains <a href="https://www.frontiersin.org/articles/10.3389/fevo.2016.00049/full">echolocation</a>.</p>
<p>A more active sense than the detection of electric or magnetic fields, echolocation involves the dolphins producing sequences of clicks with their phonic lips (located in the blowhole, the nostril on the dolphin’s head). The clicks produced are highly directional, moving forward. When the sound wave touches a surface, it returns and is perceived through the dolphin’s lower jaw. In this way, they perceive sound waves extremely well, without having external ears and so retaining their smooth hydrodynamic shape.</p>
<p>Thanks to this information, the dolphin can not only know the location of a target, but also deduce its density: a dolphin can distinguish at a distance of 75 metres whether a one-inch diameter sphere (2.54 cm) is made of <a href="https://pubs.aip.org/asa/jasa/article-abstract/68/4/1077/625152/Long-range-target-detection-in-open-waters-by-an">solid steel or filled with water</a>.</p>
<h2>Dolphins communicate through channels that are inaccessible to us</h2>
<p>Dolphins’ impressive ability to “see with their ears” doesn’t stop there. Dolphins can listen to the echoes of clicks produced by their fellow dolphins, an ability known as “eavesdropping”](https://link.springer.com/article/10.3758/BF03199007). In this way, they can “share” what they detect with the members of their group and coordinate their movements.</p>
<p>As part of my research, I was interested in <a href="https://go.gale.com/ps/i.do?id=GALE%7CA491087577">how dolphins use their clicks to synchronise their movements</a>. To do this, I exploited a <a href="https://www.aquaticmammalsjournal.org/article/vol-43-iss-2-lopez-marulanda/">recording method using four hydrophones and a 360° camera</a>, which make it possible to know which dolphin is making a sound – something that was previously impossible because dolphins do not open their mouths to vocalise.</p>
<p>I was able to show that <a href="https://www.sciencedirect.com/science/article/abs/pii/S0376635721000449">when the dolphins jump synchronously in a dolphinarium, one produces the clicks while the others remain silent</a>. In our experiment, we determined that the animal that produced the clicks was always the oldest female.</p>
<p>Will the same thing happen in the wild when dolphins fish in coordination? To find out, we would need to use the same 360° audiovisual recording method in the ocean. This would involve establishing an observation base in a feeding area with good visibility – for example, when dolphins are feeding around fish farms. The regular proximity of the dolphins would make it possible to record their solitary fishing behaviour, and to better understand how they cooperate and coordinate, using all of their three “super senses”.</p><img src="https://counter.theconversation.com/content/224884/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Juliana López Marulanda is co-founder of the Macuaticos Colombia Foundation for the research and conservation of cetaceans in Colombia.</span></em></p>Let’s delve into the three super-senses of dolphins: magnetic perception, electrical perception and echolocation.Juliana López Marulanda, Enseignante chercheuse en éthologie, Université Paris Nanterre – Université Paris LumièresLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2227672024-02-06T16:34:20Z2024-02-06T16:34:20ZWe’ve found out how earless moths use sound to defend themselves against bats – and it could give engineers new ideas<figure><img src="https://images.theconversation.com/files/573732/original/file-20240206-20-zrb59g.jpg?ixlib=rb-1.1.0&rect=26%2C40%2C4466%2C2950&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ermine moths are deaf, but have an intricate wing structure that protects them from bats by producing warning clicks when they fly.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/detailed-closeup-on-white-speckled-yponomeuta-2169581991">HWall/Shutterstock</a></span></figcaption></figure><p>An acoustic battle between <a href="https://www.annualreviews.org/doi/10.1146/annurev-ento-121510-133537">bats and their insect prey</a> has been raging in the night skies for over 65 million years. Many different techniques are used, and <a href="https://www.pnas.org/doi/10.1073/pnas.2313549121">our new study</a> reveals the fascinating strategy of the small, deaf ermine moth, which has evolved a tiny wing structure that produces warning sounds. We hope this insight could inspire engineers to create new technology.</p>
<p>Bats count on their secret weapon, <a href="https://www.bats.org.uk/about-bats/flight-food-and-echolocation">echolocation</a>, to find and catch their flying prey, and in response, nocturnal insects have evolved interesting defences. Many silk moths, for instance, rely on a kind of <a href="https://doi.org/10.1073/pnas.2014531117">sound-absorbing stealth cloak</a> that makes them “disappear” from bat sonar. Some large moth species have <a href="https://doi.org/10.1016/j.cub.2021.08.038">evolved reflective decoys</a> that draw bat attacks away from their body and towards the tips of their wings.</p>
<p>The next level of defence is <a href="https://www.annualreviews.org/doi/10.1146/annurev-ento-121510-133537">ears</a> that allow insects, including many moths, to pick up bat echolocation calls and fly out of harm’s way. They can also use their sensory awareness of location to blast an attacking bat with ultrasonic sounds that deter or confuse their biosonar. </p>
<p>However, scientists have long been puzzled about the many earless moths that cannot detect their predators and are too small for decoys. How do they protect themselves? </p>
<p>We recently discovered that <a href="https://research-information.bris.ac.uk/ws/portalfiles/portal/185355664/tymbals.pdf">even earless moths</a>, such as <a href="https://butterfly-conservation.org/moths/white-ermine">ermine moths</a> (<em>Yponomeuta</em>), use acoustic signals as a defence against bat attacks. These moths have a tiny structure in their hind wings which creates a powerful ultrasonic signal that jams the echolocating sonar of bats.</p>
<p>Because these moths don’t have hearing organs, they are not aware of their unique defence mechanism, and nor can they control it. Instead, the sound production mechanism is coupled to the flapping of their wings.</p>
<h2>Protective wing beats</h2>
<p>When we studied the ermine moth’s wing under a microscope, it became clear that one part of the wing stands out from the rest. While most of it is covered by small hairs and scales, one patch of wing is clear and located adjacent to a corrugated structure of ridges and valleys. In our new study, we found this structure produces sound perfectly tuned to confuse bats. </p>
<figure class="align-center ">
<img alt="Pipistrelle bat flying on wooden ceiling of house in darkness" src="https://images.theconversation.com/files/573422/original/file-20240205-21-ssex63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/573422/original/file-20240205-21-ssex63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/573422/original/file-20240205-21-ssex63.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/573422/original/file-20240205-21-ssex63.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/573422/original/file-20240205-21-ssex63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/573422/original/file-20240205-21-ssex63.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/573422/original/file-20240205-21-ssex63.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bats such as this pipistrelle use echolocation to hunt.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/pipistrelle-bat-pipistrellus-flying-on-wooden-1018158514">Rudmer Zwerver/Shutterstock</a></span>
</figcaption>
</figure>
<p><a href="https://dosits.org/science/sound/what-is-sound/">Sound is a pressure wave</a> that travels through a fluid or solid and requires a displacement of this medium, usually a vibration, to produce noise. Large vibrating surfaces over cavities are <a href="https://cmtext.indiana.edu/acoustics/chapter1_resonance.php">good for amplifying sound</a> – a good example is a tymbal drum, which has a taught skin stretched over a cavity. As the drum skin is struck by a drumstick, the skin vibrates at its natural frequencies and transmits these vibrations into the surrounding air as sound.</p>
<p>In ermine moths, the clear patch in the hind wing serves as the drum skin, while the corrugated structure of valleys and ridges act as drumsticks. During flight, the moth’s wing makes the ridges snap one after the other in a sequence. Each snap makes the clear patch, known as an <a href="https://research-information.bris.ac.uk/en/publications/a-bioinspired-mechanical-model-of-the-ultrasonic-clicks-produced-">aeroelastic tymbal</a>, vibrate and amplifies the sound volume.</p>
<p>Recordings we made of ermine moths found their wings make clicking noises during flight, which we could detect using a bat detector that converts ultrasound into sound audible to humans.</p>
<p>Using 3D X-ray and a sophisticated microscope technique called <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6961134/#:%7E:text=The%20primary%20functions%20of%20a,3D%20reconstructions%20of%20imaged%20samples.">confocal microscopy</a>, our study’s lead author, Hernaldo Mendoza Nava, mapped out the intricate properties of the materials that make these moths’ aeroelastic tymbals. We then used computer simulations to test our hypothesis that the deformations of the corrugations stimulate the wing’s membrane in a way that produces sound. These simulations produced a sound that matched our recordings of the moths’ clicks in frequency, structure, amplitude and direction.</p>
<p>Some eared moths can make similar warning sounds, but none of them (so far) have been shown to do this with an aeroelastic tymbal. </p>
<p>To our team of biologists and engineers, these wing structures are fascinating because they rely on a mechanism that we teach our engineering students to avoid. “Snap through” is an example of a <a href="https://www.egr.msu.edu/classes/me471/thompson/handout/class07_2005S_Buckling.pdf">buckling instability</a> – when a structure loses stability when loaded, and suddenly snaps into a different state.</p>
<p>In a buckling instability, the material doesn’t break but the structure usually loses stiffness and can even collapse. This can have catastrophic consequences for any structure that carries load, such as buildings, bridges and aeroplanes.</p>
<h2>Inspired by nature</h2>
<p>Historically, structures were made to be rigid enough to withstand external forces. Over the last decade, researchers and engineers have started to question this default position, and have begun to use buckling instabilities to create structures with new capabilities. </p>
<p>One example is engineers designing <a href="https://www.nature.com/collections/aabiaicgej#:%7E:text=Traditionally%2C%20structures%20were%20constructed%20to,and%20maintain%20its%20desired%20form.">morphing structures</a> <a href="https://www.cambridge.org/core/journals/aeronautical-journal/article/abs/morphing-skins/912AB6CFD2C2075099CC5D362D8BCB60">for future aircraft wings</a> that autonomously adapt their shape to perform better when the environment changes. The aeroelastic tymbal of ermine moths embodies this concept and demonstrates how nature can be an inspiration for new technology.</p>
<p>Our hope is that these deaf moths’ aeroelastic tymbals will encourage new developments in engineering domains such as acoustic structural monitoring, where structures give off sound when overloaded. This is often used to check the safety of infrastructure. It could also lead to innovations in <a href="https://en.wikipedia.org/wiki/Soft_robotics">soft robotics</a>, where the robots are made of fluids and gels instead of metal and plastics.</p><img src="https://counter.theconversation.com/content/222767/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marc Holderied receives funding from the Biotechnology and Biological Sciences Research Council (grant no. BB/N009991/1) and the Engineering and Physical Sciences Research Council (grant no. EP/T002654/1). We thank Diamond Light Source for access
to beamline I13 (proposal MT17616) and to Dr. Shashi Marathe and Kaz Wanelik for their assistance at the facility. We thank Daniel Robert for access to and support with Laser Doppler vibrometry.</span></em></p><p class="fine-print"><em><span>Alberto Pirrera has received funding for this research from the Engineering and Physical Sciences Research Council (grant no. EP/M013170/1).</span></em></p><p class="fine-print"><em><span>Rainer Groh has received funding from the Royal Academy of Engineering (grant no. RF/201718/17178) for this research. Hernaldo Mendoza Nava, a PhD student who worked on this project for his thesis, was funded by the Science and Technology National Council (CONACYT-Mexico, CVU/studentship no. 530777/472285) and the Engineering and Physical Sciences Research Council through the EPSRC Centre for Doctoral Training in Advanced Composites for Innovation and Science (grant no. EP/L0160208/1).</span></em></p>The ermine moth’s wing structures are fascinating because they rely on a mechanism we teach our engineering students to avoidMarc Holderied, Professor in Sensory Biology, University of BristolAlberto Pirrera, Professor of Nonlinear Structural Mechanics, University of BristolRainer Groh, Senior Lecturer in Digital Engineering of Structures, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1955932022-12-30T08:27:09Z2022-12-30T08:27:09ZFive human technologies inspired by nature – from velcro to racing cars<figure><img src="https://images.theconversation.com/files/500467/original/file-20221212-114007-p3m533.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3055%2C2024&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Many of humanity's innovations have taken inspiration from the natural world.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/great-white-shark-carcharodon-carcharias-surface-1706225779">Alessandro De Maddalena/Shutterstock</a></span></figcaption></figure><p>Nature has, over millions of years, evolved solutions to adapt to an array of challenges. As the challenges facing humanity become more complex, we are seeing inspiration being increasingly drawn from nature. </p>
<p>Taking biological processes and applying them to technological and design problems is called <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/bioinspiration">bioinspiration</a>. This is a fast-growing field, and our ability to copy nature is becoming more sophisticated. Here are five striking examples where nature has guided human innovation – and in some cases, could lead to even more exciting breakthroughs. </p>
<h2>1. Navigation</h2>
<p>Using <a href="https://www.nps.gov/subjects/bats/echolocation.htm">echolocation</a>, bats are able to fly in <a href="https://www.sciencedirect.com/science/article/pii/B9780128093245210316">complete darkness</a>. They emit sound and ultrasound waves, then monitor the time and magnitude of these waves’ reflections to create <a href="https://www.sciencedirect.com/science/article/abs/pii/S1071581907000833">three-dimensional spatial maps</a> of their surroundings. </p>
<p>The sensors that identify obstacles when reversing in many modern cars are <a href="https://www.techbriefs.com/component/content/article/tb/pub/features/articles/36374">inspired</a> by bat navigation. The direction and distance of an obstacle is calculated by emitting ultrasound waves which reflect off objects in a car’s path.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/498452/original/file-20221201-6347-cjueta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498452/original/file-20221201-6347-cjueta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498452/original/file-20221201-6347-cjueta.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498452/original/file-20221201-6347-cjueta.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498452/original/file-20221201-6347-cjueta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498452/original/file-20221201-6347-cjueta.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498452/original/file-20221201-6347-cjueta.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The echolocation concept has been adopted by many technologies in modern life, Amin Al-Habaibeh, Author provided.</span>
</figcaption>
</figure>
<p>Sensory navigation technologies have also been <a href="https://www.sciencedirect.com/science/article/pii/S1877050915031312">proposed</a> to improve the safety of those with restricted vision. Ultrasound sensors installed on the human body would offer sound-based feedback of a person’s surroundings. This would allow them to move more freely by eliminating the threat of obstacles.</p>
<h2>2. Construction equipment</h2>
<p>Woodpeckers <a href="https://www.batzner.com/resources/blog-posts/why-woodpeckers-peck-and-prevent-them-from-pecking-your-house/#:%7E:text=They%20peck%20at%20wood%20to,is%20attached%20to%20a%20building.">knock</a> on the hard surface of trees to forage for food, build nests and attract a mate. Construction tools, such as handheld hydraulic and pneumatic hammers, mimic the <a href="https://apologeticspress.org/the-jackhammer-in-your-backyard-2315/">vibrating bill of a woodpecker</a> using a frequency roughly equivalent to a woodpecker’s hammering (<a href="https://www.sciencedirect.com/science/article/abs/pii/S1672652914600457">20 to 25 Hz</a>). </p>
<figure class="align-center ">
<img alt="A woodpecker feeding chicks in its nest in a hole of a tree." src="https://images.theconversation.com/files/499263/original/file-20221206-25-zf8fph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/499263/original/file-20221206-25-zf8fph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499263/original/file-20221206-25-zf8fph.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499263/original/file-20221206-25-zf8fph.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499263/original/file-20221206-25-zf8fph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499263/original/file-20221206-25-zf8fph.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499263/original/file-20221206-25-zf8fph.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Woodpeckers knock on the hard surface of trees to forage for food, build nests and attract a mate.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/great-spotted-woodpecker-dendrocopos-major-perched-2060062277">Vaclav Matous/Shutterstock</a></span>
</figcaption>
</figure>
<p>But the vibration of these power tools can damage the hands of construction workers. This can, in some cases, cause <a href="https://www.hse.gov.uk/mvr/topics/vibration.htm">vibration white finger</a>, a condition where sufferers experience permanent numbness and pain in their hands and arms. </p>
<p><a href="https://www.sciencedirect.com/science/article/abs/pii/S0960982222009964">Research</a> is now studying how woodpeckers protect their brains from the impact of repeated drilling. One <a href="https://www.sciencedirect.com/science/article/abs/pii/S175161611830688X?via%3Dihub">study</a> found that woodpeckers have several impact-absorbing adaptions that other birds do not have. </p>
<p>Their skull is adapted to be tough and hard, and their tongue wraps around the back of the skull and anchors between their eyes. This protects a woodpecker’s brain by softening the impact of the hammering and its vibrations.</p>
<p>Research such as this is guiding the design of <a href="https://www.mdpi.com/2076-3417/11/22/10584/htm">shock absorbers and vibration control devices</a> to protect the users of such equipment. The same concept has also inspired innovations such as <a href="https://www.sciencedirect.com/science/article/pii/S2214785319341987">layered shock-absorbing structures</a> for building design.</p>
<h2>3. Building design</h2>
<p>Scallops are molluscs with a fan-shaped, corrugated external shell. The zig-zag shape of these <a href="https://www.sciencedirect.com/topics/engineering/corrugated-sheet">corrugations</a> strengthens the shell’s structure, enabling it to withstand high pressure under water.</p>
<p>The same process is used to increase the strength of a cardboard box, with corrugated paper material being glued between the two external cardboard layers. The introduction of a corrugated surface significantly increases a material’s strength, in the same way that folding a piece of paper into a zig-zag shape allows it to take an additional load.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/498782/original/file-20221204-55844-i0v9vg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498782/original/file-20221204-55844-i0v9vg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498782/original/file-20221204-55844-i0v9vg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498782/original/file-20221204-55844-i0v9vg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498782/original/file-20221204-55844-i0v9vg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498782/original/file-20221204-55844-i0v9vg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498782/original/file-20221204-55844-i0v9vg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A folded piece of paper in a zig-zag shape could withstand heavy load. Amin Al-Habaibeh, Author provided.</span>
</figcaption>
</figure>
<p>The dome-shaped structure of a scallop’s shell also enables it to withstand significant loads. This structure is self-supporting as it distributes the weight evenly over the entire dome shape, reducing the load on a single point. This improves the structure’s stability without the need for reinforcing steel beams and has inspired the <a href="https://www.sciencedirect.com/science/article/abs/pii/S0378778821003182">design of many buildings</a>, including St Paul’s Cathedral in London. </p>
<h2>4. Transport aerodynamics</h2>
<p>Sharks have two dorsal fins which provide several aerodynamic advantages. They <a href="https://dlnr.hawaii.gov/sharks/anatomy/fins-swimming/#:%7E:text=Dorsal%20fins%20stabilize%20the%20shark,and%20helping%20to%20conserve%20energy.">stabilise the shark</a> from rolling, while their aerofoil shape creates an area of low turbulence behind them and so increases the efficiency of the shark’s forward movement. </p>
<p>Shark fins have been replicated in motorised transportation. For example, racing cars use fins to both reduce turbulence when travelling at high speed and <a href="https://www.roadandtrack.com/motorsports/a28497386/shark-fin-race-car-wing-explained/">improve stability</a> when cornering. </p>
<p>Many road cars now have a small “shark fin” installed on their roof, which is used to integrate their <a href="https://natalexauto.com/blogs/natalex-auto-blog/what-is-the-shark-fin-on-the-roof-of-a-car">radio antenna</a>. This reduces drag compared to the traditional pole antenna.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/498796/original/file-20221204-55991-d268zz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498796/original/file-20221204-55991-d268zz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=336&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498796/original/file-20221204-55991-d268zz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=336&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498796/original/file-20221204-55991-d268zz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=336&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498796/original/file-20221204-55991-d268zz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=423&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498796/original/file-20221204-55991-d268zz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=423&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498796/original/file-20221204-55991-d268zz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=423&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Shark-fin antenna in a modern car. Amin Al-Habaibeh. Author provided.</span>
</figcaption>
</figure>
<p>We have also taken inspiration from nature to increase the efficiency of aircraft flight. An owl’s wings act as a <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2020.1748">suspension system</a>; by changing the position, shape and angle of their wings, they are able to <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2020.1748">reduce the effect</a> of turbulence while in flight. And <a href="https://www.nationalgeographic.co.uk/science-and-technology/2021/03/owl-wings-may-hold-the-key-to-turbulence-proof-planes">research</a> into owl flight may open the door to turbulence-free air travel in the future.</p>
<h2>5. Velcro</h2>
<p>The hook-and-loop <a href="https://www.velcro.co.uk/blog/2018/06/how-do-velcro-brand-fasteners-work/#:%7E:text=Hook%20and%20loop%20fasteners%20have,and%20loop%20fastener%20will%20be.">fastening mechanism</a> of <a href="https://www.velcro.com/news-and-blog/2016/11/an-idea-that-stuck-how-george-de-mestral-invented-the-velcro-fastener/">velcro</a> was inspired by the ability of the burrs of burdock plants to fasten to human clothing.</p>
<p>Plants use burrs to <a href="https://homeguides.sfgate.com/plants-burrs-26416.html">attach seed pods</a> to passing animals and people, in order to disperse seeds over wider areas. Burrs possess small hooks that interlock with the small loops in soft material.</p>
<p>Velcro replicates this by using a strip lined with hooks together with a fabric strip. When pressed together, the hooks attach to the loops and fasten to one another. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/498799/original/file-20221204-25475-ps5jqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498799/original/file-20221204-25475-ps5jqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=244&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498799/original/file-20221204-25475-ps5jqg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=244&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498799/original/file-20221204-25475-ps5jqg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=244&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498799/original/file-20221204-25475-ps5jqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=307&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498799/original/file-20221204-25475-ps5jqg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=307&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498799/original/file-20221204-25475-ps5jqg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=307&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hook and Loop structure under the microscope. Amin Al-Habaibeh, Author provided.</span>
</figcaption>
</figure>
<p>Velcro is used in a wide range of products worldwide. According to <a href="https://www.nasa.gov/offices/ipp/home/myth_tang.html#:%7E:text=Velcro%20was%20used%20during%20the,associated%20with%20the%20Space%20Program.">Nasa</a>, it was used in space during the Apollo missions from 1961 to 1972 to fix equipment in place in zero gravity.</p><img src="https://counter.theconversation.com/content/195593/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amin Al-Habaibeh does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Humans often look to nature for the solutions to complex problems – here are five times where biological processes have inspired innovation.Amin Al-Habaibeh, Professor of Intelligent Engineering Systems, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1930262022-11-14T00:35:22Z2022-11-14T00:35:22ZThey’re doing their best: how these 3 neighbourhood ‘pests’ deal with rainy days<figure><img src="https://images.theconversation.com/files/493996/original/file-20221108-18-x9ma6s.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C2700%2C1786&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Have you had a recent encounter with an animal you’d much rather avoid? As La Niña continues to give us rainy days, brush turkeys, bats, and cockroaches are emerging from their hide-outs. </p>
<p>We often think of them as pests, but these animals are just trying their best to cope in the heavy rain. They’re also crucial members of our urban ecosystems, and help keep the environment healthy. </p>
<p>Here’s what makes them so fascinating and important to your neighbourhood. </p>
<h2>Bats: heavy rain hinders echolocation</h2>
<p>Australia is home to multiple threatened species of <a href="https://theconversation.com/australias-threatened-bats-need-protection-from-a-silent-killer-white-nose-syndrome-129186">fruit bats and microbats</a>, such as grey-headed flying foxes, large bent-wing bats, and spectacled flying foxes. </p>
<p>They’re typically considered nuisances for their noise, mess and potential spread of diseases. But bats are often forgotten for their ability to control insect pests, disperse seeds, and pollinate plants.</p>
<p>Bats face some serious threats in La Niña conditions. They can respond to periods of heavy rain by using a special physiological adaptation called torpor. In torpor, bats will sleep more and lower their body temperature so they can use less energy.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Microbat sp. giving a smile (this bat was handled by a gloved, trained professional. Never pick up a bat yourself)</span>
<span class="attribution"><span class="source"> Image Credit Dieter Hochuli</span></span>
</figcaption>
</figure>
<p><a href="https://www.ausbats.org.au/uploads/4/4/9/0/44908845/meet_sydneys_microbats.pdf">Microbats</a> are abundant throughout Australian cities. They use <a href="https://theconversation.com/fruit-bats-are-the-only-bats-that-cant-and-never-could-use-echolocation-now-were-closer-to-knowing-why-153721">echolocation to see</a>, but heavy rain likely <a href="https://www.sciencedaily.com/releases/2019/02/190206115623.htm">reduces</a> this ability. </p>
<p>In 2019, Smithsonian researchers played recordings of downpours near bat roosts, and found the bats delayed emerging from their roosts. Delayed emergence can lead to disorientated bats with a reduced capacity to find food. </p>
<p>In Australia, rain may affect microbats more than fruit bats because of where they live. Many species of microbats, such as the <a href="https://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10534">large bent-winged bat</a>, live in culverts and under bridges, where higher water levels can rush through during heavy rain periods.</p>
<p>Fruit bats, such as flying foxes, <a href="https://theconversation.com/fruit-bats-are-the-only-bats-that-cant-and-never-could-use-echolocation-now-were-closer-to-knowing-why-153721">don’t use echolocation</a>, but rain can wet their fur and lower their body temperature. So they’ll often stay put in their roosts to keep warm during heavy rain.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fruit-bats-are-the-only-bats-that-cant-and-never-could-use-echolocation-now-were-closer-to-knowing-why-153721">Fruit bats are the only bats that can't (and never could) use echolocation. Now we're closer to knowing why</a>
</strong>
</em>
</p>
<hr>
<p>It also <a href="https://royalsocietypublishing.org/doi/10.1098/rsbl.2011.0313">costs a lot more energy</a> for a bat to fly in the rain, making it harder to maintain a steady intake of food. If there is consecutive days of rain, bats may fall from their home due to starvation. </p>
<p>If you find a fallen bat, do not touch it. Instead, contact <a href="https://www.wires.org.au/wildlife-information/flying-foxes-and-microbats">WIRES</a>. Or, wait to see if they leave once the rain clears up.</p>
<h2>Brush turkeys: reshape their mounds</h2>
<p>Brush turkeys are a type of ground nesting bird found along Australia’s east coast, from Cape York in Queensland down to Wollongong in NSW. They’re particularly vulnerable to the effects of heavy rain, which can damage or wash out their nests. </p>
<p>To incubate their eggs, brush-turkeys build enormous mounds of leaf litter and mulch. These mounds can weigh several tonnes, and can be as wide as <a href="https://www.qld.gov.au/environment/plants-animals/animals/living-with/brush-turkeys">4 metres across and up to 1 metre high</a>. These mounds often cause <a href="https://www.abc.net.au/news/2016-03-31/brush-turkeys-haunting-sydney-backyards/7287518">consternation among avid gardeners</a> and frustrated suburbanites.</p>
<p>But brush-turkeys can benefit the environment. As they <a href="https://birdlife.org.au/bird-profile/australian-brush-turkey">scratch for food and build mounds</a>, the birds help break down leaf litter and aerate the soil. This helps water and nutrients move throughout your soil, which ultimately helps your garden.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Brush-turkey on a mound.</span>
<span class="attribution"><span class="source">Image Credit Matthew Hall</span></span>
</figcaption>
</figure>
<p>Winter rainfall is the trigger for males to start building their mounds, as the increased soil moisture provides the heat that incubates their eggs. However, research shows males <a href="https://www.tandfonline.com/doi/abs/10.1071/MU9880210">avoid constructing their nests</a> during long periods of heavy rain.</p>
<p>Flood waters can sweep away existing mounds and, after multiple weeks of rain, mounds can become waterlogged. Floods can drown eggs or reduce mound temperatures below the levels necessary for incubation, preventing the chicks from developing properly. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=484&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=484&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=484&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=608&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=608&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=608&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A brush-turkey chick.</span>
<span class="attribution"><span class="source">Image Credit John Martin</span></span>
</figcaption>
</figure>
<p>Brush-turkeys are known to protect their mounds from heavy rain. Much anecdotal evidence suggests brush-turkeys can predict the weather in advance, and <a href="http://www.climatekelpie.com.au/index.php/1999/08/01/the-brush-turkeys-are-never-wrong/">reshape their mound accordingly</a>. </p>
<p>During light rain, male brush-turkeys <a href="https://www.abc.net.au/local/stories/2011/11/23/3374445.htm">open up their mound</a>, letting much-needed moisture soak in to speed up decomposition of the leaf litter. But as strong rainfall approaches, they instead <a href="https://catalogue.nla.gov.au/Record/4385974">pile extra material on top of their mound</a>, providing an extra layer of protection and creating a more conical shape so water can run off the sides. </p>
<p>Next time, consider tuning into your local brush turkeys for a weather forecast. If you see them doing a bit of extra raking in your garden on dismal grey days, it might be a scramble to protect their nests from approaching heavy rain. </p>
<p>When you spot one, use the opportunity to snap a photo and upload it to the <a href="https://taronga.org.au/conservation-and-science/current-research/big-city-birds">Big City Birds app</a>. This app tracks where birds such as brush-turkeys occur, and how they’re adapting to city life.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/sad-and-distressing-massive-numbers-of-bird-deaths-in-australian-heatwaves-reveal-a-profound-loss-is-looming-190685">‘Sad and distressing’: massive numbers of bird deaths in Australian heatwaves reveal a profound loss is looming</a>
</strong>
</em>
</p>
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<h2>Native cockroaches: evacuate to drier areas</h2>
<p>As we settle into another wet spring, our homes are becoming perfect breeding grounds for cockroaches. The humidity of a moist house combined with warmer weather, allows for cockroaches to grow quicker and thrive. </p>
<p>Only a small handful of cockroach species will survive in the average house, and they are all introduced species. After rain, it’s vital to make your house a little less cockroach friendly. Reduce humidity by keeping the house well ventilated, and make sure to remove any food scraps.</p>
<p>On the other hand, the waterlogged soil in your local green spaces are likely home to some of <a href="https://australian.museum/learn/animals/insects/cockroaches-order-blattodea/">Australia’s 450 native species of cockroaches</a>, so you might see some around your backyard after rain. Cockroaches play important roles in the ecosystem, breaking down nutrients in the soil.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=643&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=643&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=643&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=808&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=808&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=808&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Native Australian <em>Ellipsidion sp.</em> cockroach.</span>
<span class="attribution"><span class="source">Image Credit Elise Oakman</span></span>
</figcaption>
</figure>
<p>Burrowing cockroaches can be spotted because they don’t have wings. Many of our other native cockroaches are obvious due to their <a href="https://www.australiangeographic.com.au/topics/wildlife/2018/04/our-native-cockroaches-arent-as-gross-as-you-think/">beautiful colours and patterns</a>.</p>
<p>One amazing example is the <a href="https://www.sydney.edu.au/news-opinion/news/2022/10/01/extinct-wood-eating-cockroach-rediscovered-after-80-years.html">Lord Howe Island wood-feeding cockroach</a>. Thought to be extinct for some 80 years due to rats, they have only recently been rediscovered. This species is important, because it recycles nutrients and is food for other animals.</p>
<p>While native cockroaches may enter your home in an attempt to find warm dry ground, they won’t thrive indoors. If you find a native cockroach inside your house, instead of reaching for the bug spray, it’s best to catch them and put them back outside. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-large-cockroach-thought-extinct-since-the-1930s-was-just-rediscovered-on-a-small-island-in-australia-191847">A large cockroach thought extinct since the 1930s was just rediscovered on a small island in Australia</a>
</strong>
</em>
</p>
<hr>
<p>So during wet weather, take the time to remember that these animals are trying their best. All have amazing ways of adapting to heavy rain, and we should cut them some slack – the environment, including our backyards, need them.</p><img src="https://counter.theconversation.com/content/193026/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elise Oakman receives funding from the Ecological Society of Australia, the Department of Planning and Environment, and the Australian Wildlife Society.</span></em></p><p class="fine-print"><em><span>Caitlyn Forster receives funding from the Australian Research Council. She is affiliated with the Australasian Society for the Study of Animal Behaviour and Invertebrates Australia. </span></em></p><p class="fine-print"><em><span>Matthew Hall has previously received research funding from The Australian Citizen Science Association and Birding NSW. </span></em></p><p class="fine-print"><em><span>Mei-Ting Kao does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Brush turkeys, bats, and cockroaches are crucial for the environment – including our gardens. Each have fascinating ways of coping in wet weather.Elise Oakman, PhD Candidate, University of SydneyCaitlyn Forster, PhD Candidate, School of Life and Environmental Sciences, University of SydneyMatthew Hall, Casual Academic, University of SydneyMei-Ting Kao, PhD student, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1905782022-09-29T19:16:14Z2022-09-29T19:16:14ZThe night is full of animal life, but scientists know very little about it<figure><img src="https://images.theconversation.com/files/484547/original/file-20220914-18-xmkk2a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Naturalists and life scientists have long debated how insect-eating bats navigate their dark world.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bats-flying-against-sun-golden-sky-129518465">Sarun T/Shutterstock</a></span></figcaption></figure><p>Human disturbance is rapidly changing the nature of the nocturnal world. Intensive farming, suburban spread, artificially lit cities, and continuously busy road systems mean <a href="https://pubmed.ncbi.nlm.nih.gov/29903973/">daytime species</a> are becoming increasingly active throughout the night. Ecologists <a href="https://pubmed.ncbi.nlm.nih.gov/25225371/">suggest</a> that the majority of land animals are either nocturnal or active across both the day and night. </p>
<p><a href="https://theconversation.com/too-hot-to-sleep-nights-are-warming-faster-than-days-as-earth-heats-up-186958">Recent research</a> has also shown that the night is warming considerably faster than the day. The stifling night-time heat experienced across Europe this summer is indicative of this, placing nocturnal animals under even greater stress. </p>
<p>The transforming night adds new sensory pressures concerning finding food, a mate, and navigating a world permeated by artificial illumination. Environmental change is severely threatening the ability of nocturnal animals to coexist with humans. The conservation of nocturnal species has therefore become urgent. </p>
<p>Despite the abundance of night-time life, the understanding of nocturnal species has evaded science throughout history. Physical restraints on human navigation in the dark are partially responsible for this. This scientific blind spot is referred to as the “nocturnal problem”.</p>
<p>The legacy of this inaccessibility remains a barrier to our understanding of nocturnal life today. However, given the environmental threat now facing the nocturnal world, this will have profound consequences should it remain unaddressed. A better understanding of nocturnal life is critical to ensure its effective protection.</p>
<h2>The origins of the ‘nocturnal problem’</h2>
<p>So how did the nocturnal problem arise and why does it still impede science?</p>
<p>Constrained by their own reliance on vision, early scientists struggled to imagine the different ways in which animals might navigate in the dark. The myths that built up around familiar nocturnal creatures, such as hedgehogs, are evidence of historical attempts to fill the scientific gap.</p>
<p>The Greek philosopher Aristotle suggested that hedgehogs poached apples and carried them off on their spines. Such mythology was commonly included within Victorian natural history texts as an introduction to more factual descriptions of hedgehog anatomy, such as their capacity for smell and other bodily adaptations.</p>
<figure class="align-center ">
<img alt="A hedgehog passing a road with a car light illuminating the background." src="https://images.theconversation.com/files/484573/original/file-20220914-4859-6nr6ho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484573/original/file-20220914-4859-6nr6ho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484573/original/file-20220914-4859-6nr6ho.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484573/original/file-20220914-4859-6nr6ho.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484573/original/file-20220914-4859-6nr6ho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484573/original/file-20220914-4859-6nr6ho.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484573/original/file-20220914-4859-6nr6ho.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Even the experiences of hedgehogs remain to some degree unknown.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hedgehog-passing-street-night-car-lights-1280471914">Lukasz Walas/Shutterstock</a></span>
</figcaption>
</figure>
<p>But even artificial illumination afforded very limited access. Illumination fundamentally changes the nature of the nocturnal world, with impacts on animal behaviour. A good example is the attraction of moths to street lights.</p>
<p>The historical debate surrounding how insect-eating bats navigate their dark world illustrates the problem. Numerous attempts have been made to understand bat senses. However, it was not until the late 1930s, more than 150 years after experimentation on bats had begun, that the scientists Donald R. Griffin and Robert Galambos identified echolocation – the ability to navigate via the emission and detection of sound signals. </p>
<p>Griffin would later describe the secrets of bat senses as a “magic well”, acknowledging the fundamental challenge of comprehending senses so different from our own. </p>
<p>But efforts to understand nocturnal senses could only take scientists so far. In 1940, American naturalist Orlando Park declared that the biological sciences suffered from a “nocturnal problem”, in reference to the continued inability to understand the nocturnal world. This was reflected in the more recent philosophical text of Thomas Nagel, which posed the question <a href="https://warwick.ac.uk/fac/cross_fac/iatl/study/ugmodules/humananimalstudies/lectures/32/nagel_bat.pdf">what it like is to like to be a bat?</a></p>
<h2>Persistence of the nocturnal problem</h2>
<p>Despite technological developments, including the introduction of infrared photography, aspects of nocturnal life continue to elude modern science. </p>
<p>While technology has afforded scientists a much better understanding of echolocation in bats, our way of thinking about bat senses remains limited by our own dependence on vision. When describing echolocation, scientists still suggest that <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3172592/">bats “see” using echoes</a>. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1296266269008654336"}"></div></p>
<p>The elusive Australian Night Parrot was presumed extinct for much of the 20th century. Although they have been <a href="https://www.nytimes.com/2022/01/04/science/night-parrot-ghost-bird-australia.html">recently rediscovered</a>, scientists remain unable to estimate their population size accurately while questions over the threats facing the species persist. </p>
<p>Despite an improvement in scientific research, nocturnal life remains understudied. In 2019, life scientist <a href="https://www.journals.uchicago.edu/doi/full/10.1086/702250">Kevin J. Gaston</a> called for an expansion of research into nocturnal life. History shows us that when there are scientific gaps in knowledge about the night, cultures create their own truths to fill those gaps. The consequences of doing so may be significant. </p>
<p>The night is ecologically rich and efforts to fill these gaps in scientific understanding should be prioritised. The nocturnal world is threatened by environmental change, and its future depends on our commitment to getting to know the darkness.</p><img src="https://counter.theconversation.com/content/190578/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Andy Flack received funding for this research from the Arts and Humanities Research Council. The funding relates to the project 'Dark-dwellers as more-than-human misfits'.</span></em></p><p class="fine-print"><em><span>Alice Would was a Research Associate on Dr Andy Flack's AHRC Leadership Fellows Project 'dark-dwellers as more-than-human misfits.' </span></em></p>Humans have long struggled to understand the nocturnal world. As environmental change becomes increasingly acute, understanding their lives has never been more critical.Andy Flack, Senior Lecturer in Modern and Environmental History, University of BristolAlice Would, Lecturer in Imperial and Environmental History, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1756732022-02-21T12:30:59Z2022-02-21T12:30:59ZMoths and bats have been in an evolutionary battle for millions of years – and we’re still uncovering their tricks<figure><img src="https://images.theconversation.com/files/445412/original/file-20220209-25-wpmyla.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C3003%2C1994&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Moths have evolved extraordinary tricks to fend off bat attacks.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Todd_Cravens_2017_(Unsplash).jpg">Todd Cravens/Wikimedia</a></span></figcaption></figure><p>There aren’t many better examples of two species embroiled in an intense struggle for survival than bats and moths. These two animals are the archetype of an <a href="https://theconversation.com/explainer-the-evolutionary-arms-race-between-bats-and-moths-43675">evolutionary arms race</a>, with each trying to one-up the other in the battle of survival between predator and prey.</p>
<p>Bats first evolved the ability to <a href="https://www.discoverwildlife.com/animal-facts/what-is-echolocation/">echolocate</a> around 65 million years ago. By producing high frequency “clicks” with their mouth or nose and listening for echoes bouncing off objects, bats are able to illuminate the world around them with sound.</p>
<p>Echolocation allows bats to exploit hunting opportunities unavailable to other aerial predators. By hunting at night, they have the opportunity to pursue and consume nocturnal insects. </p>
<p>This ability has put huge pressure on the insects that bats target, such as crickets, lacewings and grasshoppers. That means many of these insects have evolved an extraordinary range of <a href="https://www.bionity.com/en/encyclopedia/Adaptation.html">counter-adaptations</a> to help them survive. And in no species are these so evident as in moths.</p>
<p>Many moths have evolved ears that are sensitive to bat echolocation calls. This allows them to hear bats approaching and take evasive action, like hiding in foliage or flying away. </p>
<p>Some moths have even <a href="https://prelights.biologists.com/highlights/anti-bat-ultrasound-production-in-moths-is-globally-and-phylogenetically-widespread/">evolved</a> to produce sounds of their own, alerting bats that they are toxic. If a species emits high frequency clicks that are audible to an attacking bat, the bat will quickly learn to associate a clicking moth with a bad taste: and will stop targeting them altogether. </p>
<p>The clicks of some moth species are even able to “jam” bats’ echolocation calls. By timing their clicks to overlap with the clicks of an approaching bat, moths are able to confuse the bat, making it harder for it to reach its target.</p>
<h2>Absorbing sound</h2>
<p>At the <a href="https://research-information.bris.ac.uk/en/persons/thomas-r-neil">University of Bristol</a>, my colleagues and I are most interested in the defences of moths that don’t have ears. If they can’t hear an approaching bat, how might they increase their chances of survival? Moths without ears would have to have evolved <a href="https://www.nature.com/articles/srep35600">passive defences</a>, meaning adaptations that are present all the time, regardless of whether a moth is under threat from a nearby bat or not. </p>
<p>Recently, we’ve uncovered two such adaptations in moth species without ears. The first is <a href="https://www.nature.com/articles/news980827-6">acoustic camouflage</a>. This is the sound equivalent of visual camouflage: when an octopus <a href="https://www.youtube.com/watch?v=PmDTtkZlMwM">blends perfectly</a> into a rock, or an insect looks <a href="https://www.youtube.com/watch?v=C7R_Zjz1IoI">exactly like</a> a leaf.</p>
<figure class="align-center ">
<img alt="A beige-coloured moth" src="https://images.theconversation.com/files/446479/original/file-20220215-23-zihx8x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446479/original/file-20220215-23-zihx8x.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446479/original/file-20220215-23-zihx8x.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446479/original/file-20220215-23-zihx8x.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446479/original/file-20220215-23-zihx8x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446479/original/file-20220215-23-zihx8x.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446479/original/file-20220215-23-zihx8x.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Antheraea pernyi, a species of earless moth, has evolved sound-absorbent wings that act as acoustic camouflage.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>To achieve this, earless moths have evolved <a href="https://www.newscientist.com/article/2260621-earless-moths-have-acoustic-camouflage-that-protects-them-from-bats/">specialised scales</a> on their wings and body that absorb sound energy from an echolocating bat, causing the bat to receive a diminished echo from the moth’s body. By dampening the sound in this way, the moth is able to literally disappear from an echolocating bat’s “view” of the night sky.</p>
<p>The way that these scales are able to absorb sound is quite spectacular. Each scale on a moth wing vibrates in response to sound waves, but the scales all vibrate at slightly different frequencies. So working together, the scales are able to absorb sound at all the <a href="https://dnr.maryland.gov/wildlife/Pages/plants_wildlife/bats/batelocu.aspx">frequencies</a> bats use for hunting, which span from 11 kilohertz to 212 kilohertz. </p>
<p>By vibrating, the scales dissipate sound energy by converting it to kinetic energy and heat. The lessons we’ve learned from these scales will hopefully help us create thinner <a href="https://www.acoustiblok.co.uk/soundproofing-materials/">sound-absorbing</a> materials to line walls of buildings like music studios and buildings on busy residential roads, making the world a quieter place for all.</p>
<h2>Diverting attacks</h2>
<p>Another adaptation we’ve identified in moths is an <a href="https://scitechdaily.com/moth-wingtips-structured-to-reflect-sound-an-acoustic-decoy-to-thwart-bat-attack/">acoustic decoy</a>. This can be thought of as the sound equivalent to <a href="https://www.nhm.ac.uk/discover/why-do-butterflies-have-eyespots.html">eyespots</a> seen in fish and butterflies. The idea is to divert a predator’s attack away from the vital body parts of an animal, such as their head, towards more expendable appendages like fins and wings that could be lost without fatal damage. </p>
<p>In moths, these decoys take the form of elongated, twisted structures on the wingtips. Some moths also have long hindwings that end in a similar shape, known as streamer decoys. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/446481/original/file-20220215-15-x7febc.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing examples of streamer decoys in two different moth species" src="https://images.theconversation.com/files/446481/original/file-20220215-15-x7febc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446481/original/file-20220215-15-x7febc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=569&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446481/original/file-20220215-15-x7febc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=569&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446481/original/file-20220215-15-x7febc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=569&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446481/original/file-20220215-15-x7febc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=716&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446481/original/file-20220215-15-x7febc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=716&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446481/original/file-20220215-15-x7febc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=716&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Examples of streamer decoys in two different moth species.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The unique, undulating shape of these structures means that these body parts are excellent at reflecting sound, as well as scattering it over many different angles. Our research has shown that bats will attack these <a href="https://rosarubicondior.blogspot.com/2021/09/unintelligent-designer-news-batty.html">streamers</a> rather than the vulnerable body of the moth itself. This makes it more likely for moths to survive bat attacks and live another day. </p>
<p>As we uncover new and fascinating tricks like these, it’s likely that we’re only just beginning to understand all the adaptations that these species have evolved. There is already some <a href="https://www.popsci.com/animals/bat-ear-echolocation-evolution/">evidence</a> that bats have changed their echolocation calls to sneak up on insects that have ears, whilst it remains to be seen if they can overcome other forms of defence such as acoustic camouflage. It seems moths currently have the upper hand in this arms race, but bats probably have a few tricks up their wings to fight them.</p><img src="https://counter.theconversation.com/content/175673/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Neil receives funding from Engineering and Physical Sciences Research Council (EPSRC) . </span></em></p>Research has revealed how earless moths manage to avoid bat attacks - by evolving sophisticated acoustic tricks.Thomas Neil, Postdoctoral Research Associate in Biological Sciences, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1682172021-09-20T14:51:21Z2021-09-20T14:51:21ZMoths use acoustic decoys to dodge bat attacks – new research<figure><img src="https://images.theconversation.com/files/422114/original/file-20210920-23-ls2chl.jpeg?ixlib=rb-1.1.0&rect=2%2C2%2C1329%2C1075&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/schreibers-bat-miniopterus-schreibersii-flight-hunting-1222783126">Agami Photo Agency/Shutterstock</a></span></figcaption></figure><p>In dark skies around the world there unfolds a nightly battle between bats and the nocturnal insects upon which they feast. You’d have thought bats, equipped as they are with echolocation, in which they navigate using sound, would have no trouble gobbling up the apparently clueless insects you see banging against your windows after dusk.</p>
<p>But bats evolved their ultrasonic sensitivity <a href="https://pubmed.ncbi.nlm.nih.gov/21888517/">65 million years ago</a>. That’s more than enough time for natural selection to kick in on the behalf of insects, leading to a host of evolutionary defences that are particularly prevalent and diverse among moths.</p>
<p>Bats have responded to these adaptations in what has become a <a href="https://theconversation.com/explainer-the-evolutionary-arms-race-between-bats-and-moths-43675">co-evolutionary arms race</a> between predator and prey. Some have <a href="https://link.springer.com/article/10.1007%25252Fs00442-002-1107-1">shifted the frequency</a> of their calls to parts of the spectrum that a moth isn’t sensitive to. Other have <a href="https://www.sciencedirect.com/science/article/pii/S0960982210009917">decreased the amplitude</a> of their calls – essentially “whispering” as they hunt so as to not alert the moth of an impending attack.</p>
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Read more:
<a href="https://theconversation.com/explainer-the-evolutionary-arms-race-between-bats-and-moths-43675">Explainer: the evolutionary arms race between bats and moths</a>
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<p><a href="https://www.sciencedirect.com/science/article/abs/pii/S0960982221011428">Our recent research</a> has shed light on a particularly unusual technique that silk moths have evolved to come away unscathed from a bat attack: the use of acoustic decoys. Deployed on their wingtips, these throw bats off the scent – or rather the sound – of moths’ bodies, helping them to survive the majority of their encounters.</p>
<h2>Evasive action</h2>
<p>Most moths are nocturnal, which means they rest during the day and are active at night. That helps them evade the attention of birds, but not the bats with which they share the night sky. </p>
<p>So moths have had to develop a unique defensive arsenal against their shadowy assailants. Many moths have evolved <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-3032.2000.00204.x">ultrasound-sensitive hearing</a>, allowing them to detect an approaching bat and take evasive action. Others have developed the ability to produce ultrasonic clicks of their own, warning a bat of their <a href="https://www.nature.com/articles/s41598-018-37812-z">unpalatability</a> – or even <a href="https://www.science.org/lookup/doi/10.1126/science.1174096">jamming the bat’s sonar</a> so they can’t hunt effectively.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/MgRh_Q_xwys?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>Many moths have also evolved passive defences which protect them even if they’re unaware of nearby bats. One such defence is acoustic camouflage. Our lab has demonstrated that <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsif.2019.0692">thorax scales</a>, on the bulbous middle part of a moth’s body, are incredibly good sound absorbers. That means the ultrasonic calls of bats return less of an echo from the moth’s body, allowing the insect to disappear silently into the night sky. </p>
<p>More recently, we’ve shown that scales on <a href="https://www.pnas.org/content/117/49/31134.short">moths’ wings</a> provide an equivalent protective benefit, with individual scales vibrating at different frequencies used by hunting bats, dissipating the sound energy used in echolocation. That finding qualified moths’ wings as the first known naturally occurring <a href="https://www.science.org/doi/10.1126/sciadv.1501595?utm_campaign=TrendMD_1&utm_medium=cpc&utm_source=TrendMD">acoustic metamaterial</a>, where interacting sub-units create acoustic properties exceeding the sum of their parts.</p>
<h2>A wing and a prayer</h2>
<p>Other moths take a different approach, amplifying rather than deafening the echo that resounds off their wings. These moths don’t have a death wish; they’re throwing out acoustic decoys to make bats target their wingtips rather than their more vulnerable bodies. </p>
<p>Acoustic decoys have previously been identified on the elongated <a href="https://www.pnas.org/content/112/9/2812.short">hindwing tails</a> of some silk moths, which end in a twisted structure that produces strong echoes when hit with ultrasound. By deflecting a bat’s attack towards the hindwings, studies have shown these moths can survive <a href="https://www.science.org/doi/10.1126/sciadv.aar7428">around 70%</a> of bat attacks.</p>
<p>Our <a href="https://www.sciencedirect.com/science/article/abs/pii/S0960982221011428">recent study</a> looked at the curiously rippled and folded wingtips on silk moths’ forewings. We postulated that these structures might serve the same protective function as the elongated hindwings identified in other silk moths.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/422126/original/file-20210920-17-10a5xnz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The location of acoustic decoy on different moths' wings" src="https://images.theconversation.com/files/422126/original/file-20210920-17-10a5xnz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422126/original/file-20210920-17-10a5xnz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=552&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422126/original/file-20210920-17-10a5xnz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=552&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422126/original/file-20210920-17-10a5xnz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=552&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422126/original/file-20210920-17-10a5xnz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=694&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422126/original/file-20210920-17-10a5xnz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=694&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422126/original/file-20210920-17-10a5xnz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=694&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Acoustic decoys are generated at the wingtip to dodge bat attacks.</span>
<span class="attribution"><span class="source">Thomas R Neil</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>To test this, we used innovative acoustic tomography to map the regions of a moth’s body and wings that produce the strongest echoes. We hit moth specimens with ultrasound and recorded the echoes, much like how a bat would locate their prey using echolocation. </p>
<p>By doing this from thousands of different angles, we created an image of a moth using sound. This revealed exactly which parts of a moth produce loud echoes and which parts produce weaker echoes. </p>
<figure class="align-center ">
<img alt="An image showing a moth' forewing tip imaged tomographically" src="https://images.theconversation.com/files/422123/original/file-20210920-21-8i03wq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422123/original/file-20210920-21-8i03wq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=346&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422123/original/file-20210920-21-8i03wq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=346&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422123/original/file-20210920-21-8i03wq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=346&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422123/original/file-20210920-21-8i03wq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=434&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422123/original/file-20210920-21-8i03wq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=434&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422123/original/file-20210920-21-8i03wq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=434&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tomographic imaging of the silk moth, with red indicating stronger echoes.</span>
<span class="attribution"><span class="source">Thomas R Neil</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We tested nine species of moth with varying forewing structures, finding that in the most elaborately shaped moths, the wingtip produced consistently stronger echoes than the body, with an echo strength difference of up to ten decibels.</p>
<p>Next, we wanted to explore the topology of these wingtips to understand how these strong echoes are created. Using a surface-scanning microscope, we identified two types of so-called “<a href="https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.105202">acoustic retroreflectors</a>” - structures that are shaped in such a way that they always send sound back to its source, regardless of which angle the sound hit at. </p>
<figure class="align-center ">
<img alt="A diagram showing where retroreflection takes place on moth wingtips" src="https://images.theconversation.com/files/422130/original/file-20210920-28-3tlzi4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422130/original/file-20210920-28-3tlzi4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=383&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422130/original/file-20210920-28-3tlzi4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=383&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422130/original/file-20210920-28-3tlzi4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=383&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422130/original/file-20210920-28-3tlzi4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=481&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422130/original/file-20210920-28-3tlzi4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=481&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422130/original/file-20210920-28-3tlzi4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=481&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We found two different types of retroreflectors on silk moth wingtips.</span>
<span class="attribution"><span class="source">Thomas R Neil</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Retroflectors work by reflecting sound back to its source through multiple reflections within themselves. It’s a complex mechanism that reveals the extraordinary decoy functionality that has evolved in moth’s wings to put off attacking bats.</p>
<p>The discovery of acoustic decoys helps shed more light on the night-time arms race between bats and moths. Whether bats will be able to counter these deceptive adaptions with enhanced weaponry of their own remains to be seen.</p><img src="https://counter.theconversation.com/content/168217/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marc Holderied receives funding from Engineering and Physical Sciences Research Council (Grant EP/T002654/1).</span></em></p><p class="fine-print"><em><span>Thomas R Neil receives funding from the EPSRC. </span></em></p>These nocturnal insects have amassed an impressive defensive arsenal against bats’ echolocation.Marc Holderied, Professor in Sensory Biology, University of BristolThomas Neil, Postdoctoral Research Associate, School of Biological Sciences, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1539392021-02-09T13:31:19Z2021-02-09T13:31:19ZScientists at work: New recordings of ultrasonic seal calls hint at sonar-like abilities<figure><img src="https://images.theconversation.com/files/382875/original/file-20210207-18-1wwb8n2.jpg?ixlib=rb-1.1.0&rect=75%2C42%2C2766%2C1697&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientist and seal, under the Antarctic ice.</span> <span class="attribution"><span class="source">McMurdo Oceanographic Observatory</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/382838/original/file-20210206-17-q3qr1u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="SCUBA divers sit around a square hole cut in Antarctic ice" src="https://images.theconversation.com/files/382838/original/file-20210206-17-q3qr1u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/382838/original/file-20210206-17-q3qr1u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382838/original/file-20210206-17-q3qr1u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382838/original/file-20210206-17-q3qr1u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382838/original/file-20210206-17-q3qr1u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382838/original/file-20210206-17-q3qr1u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382838/original/file-20210206-17-q3qr1u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Divers inside the shelter hut prepare to drop into the ocean.</span>
<span class="attribution"><span class="source">McMurdo Oceanographic Observatory</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>I’m sitting on the edge of a hole drilled through 15 feet of Antarctic sea ice, about to descend into the frigid ocean of the southernmost dive site in the world. I wear nearly 100 pounds of gear – a drysuit and gloves, multiple layers of insulation, scuba tank and regulators, lights, equipment, fins and over 40 pounds of lead to counteract all that added buoyancy.</p>
<p>I do a final check with my dive buddies: Air? Hoses? Weights? Then, one by one, we put in our mouthpieces, plop into the hole and sink out of sight into the dark.</p>
<p>As we frog-kick along, following our lights toward the work site, <a href="http://weddellsealscience.com/">a Weddell seal glides by</a> with a few effortless undulations. It glances sideways at us a couple of times, as if doing a double-take.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382841/original/file-20210206-17-2c0iz3.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Weddell seal swims by SCUBA diver with scientific equipment" src="https://images.theconversation.com/files/382841/original/file-20210206-17-2c0iz3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382841/original/file-20210206-17-2c0iz3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382841/original/file-20210206-17-2c0iz3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382841/original/file-20210206-17-2c0iz3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382841/original/file-20210206-17-2c0iz3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382841/original/file-20210206-17-2c0iz3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382841/original/file-20210206-17-2c0iz3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A Weddell seal swims by as Paul Cziko works.</span>
<span class="attribution"><span class="source">McMurdo Oceanographic Observatory</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In contrast to us awkward, gear-laden human divers, Weddell seals are completely at home under the ice. They can hold their breath for over 80 minutes and dive to a depth of nearly 2,000 feet. Somehow they explore, find food and return to their isolated breathing holes even when it’s completely dark.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/382840/original/file-20210206-21-181rvme.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Exit hole for divers cut through 15 feet of ice" src="https://images.theconversation.com/files/382840/original/file-20210206-21-181rvme.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/382840/original/file-20210206-21-181rvme.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382840/original/file-20210206-21-181rvme.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382840/original/file-20210206-21-181rvme.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382840/original/file-20210206-21-181rvme.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382840/original/file-20210206-21-181rvme.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382840/original/file-20210206-21-181rvme.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There’s just one way out for the research divers.</span>
<span class="attribution"><span class="source">McMurdo Oceanographic Observatory</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We, on the other hand, have about 30 minutes of bottom time before our hands get too cold to work. Then we make our way back to the dive line. Its flags and blinking lights guide us to our one and only way out.</p>
<p>During my deployment to Antarctica in 2018, I participated in 40 such dives to help maintain the <a href="https://moo-antarctica.net/">McMurdo Oceanographic Observatory</a>. Polar marine biologist <a href="https://scholar.google.com/citations?user=Zn3asugAAAAJ&hl=en&oi=ao">Paul Cziko</a> installed the 70-foot-deep, seafloor-mounted recorder in 2017. Known affectionately as “MOO,” it resembled R2-D2 in both looks and charm. For two years, MOO successfully sent continuous audio, video and ocean data back to our onshore lab via cable connection. It also streamed a real-time view of this enthralling Antarctic marine ecosystem: ice glittering on the seafloor and ceiling, <a href="https://www.sciencemag.org/news/2020/09/creepy-sea-spiders-have-evolved-be-tough">giant sea spiders</a> and isopods creeping among the sponges and soft corals.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382839/original/file-20210206-20-1htjv2x.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="SCUBA diver accesses underwater recording equitpment" src="https://images.theconversation.com/files/382839/original/file-20210206-20-1htjv2x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382839/original/file-20210206-20-1htjv2x.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382839/original/file-20210206-20-1htjv2x.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382839/original/file-20210206-20-1htjv2x.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382839/original/file-20210206-20-1htjv2x.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382839/original/file-20210206-20-1htjv2x.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382839/original/file-20210206-20-1htjv2x.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The McMurdo Oceanographic Observatory, mounted to the seafloor, 70 feet below the Antarctic ice.</span>
<span class="attribution"><span class="source">McMurdo Oceanographic Observatory</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Seals were only occasionally caught on camera, but their haunting calls dominated the soundscape. Although the initial goal of the MOO was to support research on the <a href="https://www.openaccessgovernment.org/antarctic-notothenioid-fishes/41433/">ice-adapted fishes native to the area</a>, analysis of the audio recordings led us to a surprising discovery. <a href="https://doi.org/10.1121/10.0002867">Weddell seals produce ultrasonic calls</a> – sequences of chirps and whistles with frequencies well above 20 kHz, the upper limit of human hearing. </p>
<h2>Surprising seal sounds</h2>
<p>These newly discovered call types – nine in total, with base frequencies above 20 kHz and ranging up to nearly 50 kHz – are the first report of such high-frequency vocalizations in any wild seals, sea lions and walruses, the group of sea mammals collectively known as pinnipeds.</p>
<p>Although scientists have studied Weddell seals for many decades and <a href="https://www.researchgate.net/publication/258836261_Quantitative_analysis_of_the_underwater_repertoire_of_the_Weddell_seal_Leptonychotes_weddellii">described much of their diverse vocal repertoire</a>, acoustic recording has historically been limited by time and equipment constraints. Most prior studies sampled within the human-audible range only for short stints during the Antarctic field season.</p>
<p>The MOO was the first long-term observatory of its kind, and its cutting-edge technology let us collect an unprecedented data set, including sounds with frequencies up to about 10 times higher than most previous studies.</p>
<p>Our discovery begs the question: What do the seals use their high-pitched ultrasonic calls for? One possibility is that they represent a form of active biosonar, similar to the <a href="https://doi.org/10.1007/978-1-4614-9146-0_1">echolocation used by bats and dolphins</a>. That is, the returning echoes of their high-frequency sounds may provide information to the seals about their environment and potential prey.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/NE-sNx1R2L4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Weddell seal producing ultrasonic vocalizations in McMurdo Sound, Antarctica.</span></figcaption>
</figure>
<p>Previous studies have <a href="https://doi.org/10.1121/1.428506">argued that pinnipeds do not echolocate</a> because they do not possess the specialized anatomy for producing or processing tightly focused sounds with very short time intervals. Additionally, their known calls don’t exhibit the telltale characteristics of echolocation pulses, such as accelerating in time as an animal approaches a target.</p>
<p>But the ability to use sound to “see” their surroundings would be especially useful during very low-visibility conditions – like what the seals encounter under thick ice or in the polar winter, when there is no daylight for four months. Our preliminary findings indeed suggested that the use of certain high-frequency pulsed vocalizations increased during the dark Antarctic winter. It is also very likely, and not mutually exclusive, that the seals use ultrasonic calls for communication, as <a href="https://doi.org/10.1139/z83-194">has been shown for their human-audible calls</a>.</p>
<h2>Serendipitous discovery raises more questions</h2>
<p>It’s still a mystery how seals navigate and forage under the ice in certain conditions. Weddell seals and other seals that live on the ice <a href="https://doi.org/10.1016/j.dsr2.2012.07.006">have many adaptations</a> for diving and <a href="https://doi.org/10.1139/z92-238">finding their breathing holes again</a>, including good low-light vision, spatial memory and extremely sensitive whiskers, called vibrissae.</p>
<p>However, these senses each have their limitations. Sometimes there may be literally no ambient light where the seals are diving. Following the same routes on every dive would preclude finding new patches of mobile prey. And the tactile sensation provided by whiskers is only useful at close range.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382836/original/file-20210206-17-1o3tql4.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Weddell seal" src="https://images.theconversation.com/files/382836/original/file-20210206-17-1o3tql4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382836/original/file-20210206-17-1o3tql4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382836/original/file-20210206-17-1o3tql4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382836/original/file-20210206-17-1o3tql4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382836/original/file-20210206-17-1o3tql4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382836/original/file-20210206-17-1o3tql4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382836/original/file-20210206-17-1o3tql4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Weddell seals swim in challenging conditions.</span>
<span class="attribution"><span class="source">McMurdo Oceanographic Observatory</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>It seems obvious that seals would also use sound to gain information about their surroundings. Indeed, Weddell seals and other related species can <a href="https://doi.org/10.1007/s00359-013-0813-y">hear frequencies up to at least 60 kHz</a>, and researchers have found that seals use acoustic cues, when available, <a href="https://doi.org/10.1139/z92-238">to navigate</a>. However, actively emitting high-frequency chirps and interpreting their own echoes would definitely be a step beyond passive listening.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p>Back in the lab <a href="https://www.usap.gov/videoclipsandmaps/mcmwebcam.cfm">at McMurdo Station</a>, the MOO livestream ran as we worked at our desks. The ethereal trills and chirps of seals filled the air. During their Southern Hemisphere spring breeding season, vocal activity is nearly constant. A couple of monitors showed real-time graphical displays of the incoming data: ocean temperature, salinity, tides. A scrolling audio spectrogram would pull us in every so often, mesmerizing us with colorful squiggles that appeared as we heard the calls – a synchronized visual soundtrack.</p>
<p>Every few minutes, bright wiggles and lines would scroll by in the upper register, announcing sounds that we cannot hear. They are patterned; they are repeated again and again. They are seal voices. If we can decode them, they may tell us <a href="https://doi.org/10.1007/s00227-020-03730-w">more about how these seals thrive</a> in what we humans perceive to be a very challenging environment. As technology sheds new light into the depths, what else will we find?</p><img src="https://counter.theconversation.com/content/153939/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lisa Munger does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Microphones on the seafloor recorded life under the Antarctic ice for two years – inadvertently catching seal trills and chirps that are above the range of human hearing. Could they be for navigation?Lisa Munger, Instructor of Natural Sciences, University of OregonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1466742020-09-23T04:35:21Z2020-09-23T04:35:21Z‘Like trying to find the door in a dark room while hearing your relatives scream for help’: Tasmania’s whale stranding tragedy explained<p>A desperate rescue effort is underway after hundreds of long-finned pilot whales (<em>Globicephala melas</em>) became stranded in Macquarie Harbour on Tasmania’s west coast. </p>
<p>Yesterday, more than 250 pilot whales <a href="https://www.bbc.com/news/world-australia-54244499">were reported</a> to have stranded, with one-third presumed dead. And this morning, rescuers found <a href="https://www.sbs.com.au/news/another-200-pilot-whales-found-stranded-on-tasmania-s-remote-west-coast">another 200 pilot whales</a> stranded up to ten kilometres away from the first group — most are likely dead. </p>
<p>This brings the total number of stranded pilot whales in Tasmania to more than 450, and it’s believed to be the biggest ever recorded in the state. The Greens are calling on federal Environment Minister Sussan Ley to launch a national response.</p>
<p>The rescue mission aims to refloat the pilot whales that appear to still be in reasonable health. But their behaviour hampers rescue efforts: many pilot whales re-strand themselves to be with their family. This event likely means a number of generations of the local population will be lost.</p>
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<strong>
Read more:
<a href="https://theconversation.com/do-whales-attempt-suicide-50165">Do whales attempt suicide?</a>
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<h2>How did they become stranded?</h2>
<p>Despite its name, the long-finned pilot whale is actually a large oceanic dolphin. They cover <a href="https://oceana.org/marine-life/marine-mammals/long-finned-pilot-whale">vast areas</a> of the Southern (Antarctic) Ocean, reaching between four and six metres in length and weighing up to one tonne. </p>
<p>They are well adapted to deeper oceans where <a href="https://www.nature.com/articles/s41598-019-51619-6">they hunt</a> for various species of squid in depths of between 600-1,000m, using echolocation to find their prey. Echolocation is a way of using sound to navigate in complete darkness. </p>
<p>They generally spend most of their lives offshore and it’s not well understood what conditions drive them close to shore, and to enter shallow embayments. </p>
<p>Some theories suggest food shortages are to blame, or changes in electromagnetic fields that disorient them. They may also be following a sick or distressed pod leader. And <a href="https://www.smh.com.au/environment/conservation/strong-association-found-between-whale-strandings-and-use-of-naval-sonar-20200219-p5428a.html.">in some past cases</a> strandings were related back to active sonar from ships and naval sonar interrupting their echolocation. </p>
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Read more:
<a href="https://theconversation.com/what-causes-whale-mass-strandings-72985">What causes whale mass strandings?</a>
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<p>But once in shallow waters, it’s difficult to swim back out. As these whales mostly navigate with echolocation it’s not possible for them to use sonar effectively in shallow and muddy embayments. </p>
<p>It’s extremely distressing for the whales, a lot like trying to find the door in a dark room while hearing your relatives scream for help. </p>
<p>In fact, the stress is what many die from in the end. Other causes of death are overheating from sun exposure and drowning if they can’t move their bodies up to breach the surface in shallow water. </p>
<h2>The rescue efforts</h2>
<p>There are a <a href="https://www.bbc.com/news/world-asia-38939799">number of strategies</a> to refloat whales. In Macquarie Harbour, rescuers are using slings to tow the whales to deeper water, before releasing them. </p>
<p><a href="https://www.stuff.co.nz/nelson-mail/news/89265113/mass-whale-stranding-at-farewell-spit">Other options</a> include multiple people pushing them off the beach during high tide into deeper water. </p>
<p>In this case, albeit potentially dangerous for the helpers, people power can make a big difference. After all, time is of immense importance for success, and to stop more whales beaching. </p>
<p>However, chances of survival plummet with long exposure to sun and extended periods of stress. What’s more, Macquarie Harbour is relatively remote and difficult to access, further complicating rescue efforts. </p>
<h2>Dying together</h2>
<p>But the biggest obstacle rescuers face is the whales’ social bonding. Long-finned pilot whales are highly intelligent and live in <a href="https://brill.com/view/journals/beh/154/5/article-p509_1.xml">strong social units</a>. </p>
<p>So when dealing with mass strandings, it’s important to realise the emotions and bonding between the whales are very likely beyond what humans can feel. One well-documented example of their emotional depth is the pilot whale seen <a href="https://www.youtube.com/watch?v=0a8HGJid-Jo">carrying its dead calf</a> for many days.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/0a8HGJid-Jo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Mother pilot whale grieves over her dead calf.</span></figcaption>
</figure>
<p>This makes the stranding process extremely complex, as it unfolds over several hours to several days — the whales don’t all strand at the same time. </p>
<p>We know from killer whales, which also have strong social bonding, that if a close member of the group strands, <a href="https://www.abc.net.au/news/2013-07-03/stranded-killer-whales-die-off-queenslands-fraser-island/4796904">others will attempt to join</a> to <a href="https://theconversation.com/do-whales-attempt-suicide-50165">die together</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-need-to-understand-the-culture-of-whales-so-we-can-save-them-123884">We need to understand the culture of whales so we can save them</a>
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</em>
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<p>The situation for pilot whale pods can be similar, but more complex as a result of having much larger pods. Pilot whale pods have multiple sub-units, which can consist of friends as well as family and they don’t have to be genetically related. </p>
<p>Social units get mixed up when they’re in shallow bays. This means individuals can <a href="https://www.sciencedaily.com/releases/2013/03/130314124603.htm">become disconnected</a> from their social units before the actual stranding occurs, causing stress and confusion prior the beaching. </p>
<h2>Fewer pilot whales in the gene pool</h2>
<p>There are <a href="https://www.fisheries.noaa.gov/species/long-finned-pilot-whale">an estimated</a> 200,000 long-finned pilot whales in the Southern Ocean and Antarctica, but mass strandings like this can have a profound impact on sub-populations. </p>
<p>In Tasmania alone, <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0206747">1,568 long-finned pilot whales</a> have stranded between 1990 and 2008 in 30 stranding events. </p>
<p>Many similar sad events <a href="https://www.doc.govt.nz/news/media-releases/2018/mass-pilot-whale-stranding-at-rakiurastewart-island/">occured in New Zealand</a>: hundreds of long-finned pilot whales stranded in 2018 and 2017, and <a href="https://www.newscientist.com/article/2120967-400-pilot-whales-stranded-on-new-zealands-whale-trap-beach/">the majority</a> died. </p>
<p>To make matters worse, studies suggest the long-finned pilot whales in the Southeastern Pacific have low genetic diversity. There are similarities between this species found in Chile and New Zealand, but with surprisingly <a href="https://www.nature.com/articles/s41598-020-58532-3">distinct differences</a> between New Zealand and Tasmania. </p>
<p>Considering they can live up to 50 years and the fact only few survive when multiple generations strand, such events not only destroy entire generations but also remove them from the gene pool. </p>
<p>This puts local populations at further risk. Inbreeding is one consequence, but the biggest problem is their decreasing general fitness and ability to adapt to changes.</p>
<h2>How to help</h2>
<p>In the past, significant numbers of stranded whales have been successfully released, making it worth the effort. For example, in one of largest mass strandings in New Zealand in 2017, volunteers helped about 100 whales <a href="https://www.doc.govt.nz/news/media-releases/2017/whale-rescue-effort-continues/">refloat</a>, and made a human chain to try to stop them restranding. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-time-to-speak-up-about-noise-pollution-in-the-oceans-64672">It's time to speak up about noise pollution in the oceans</a>
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<p>Still, such events are likely to be more frequent in the future due to changing ocean conditions and increasing human activity such a noise pollution, commercial squid fisheries and deep sea mining. </p>
<p>Climate change <a href="https://tos.org/oceanography/article/southern-ocean-warming">shifts ocean currents</a> as sea temperature rises. And with this, squid availability will change. A <a href="https://www.jstor.org/stable/24857467?seq=1#metadata_info_tab_contents">lack of food</a> offshore can cause stress and drive them closer to shore.</p>
<p>We can help the whales not only by actively supporting rescue organisations such as <a href="http://www.orrca.org.au/">ORRCA</a>, but also by helping reduce carbon emissions, foster sustainable fisheries, reduce plastic pollution and advocate for marine sanctuaries.</p><img src="https://counter.theconversation.com/content/146674/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Olaf Meynecke receives funding from a private charitable trust, and is the CEO of the not-for-profit organisation Humpbacks and Highrises. </span></em></p>More than 450 long-finned pilot whales are stranded in Tasmania. Saving them is a race against time.Olaf Meynecke, Research Fellow in Marine Science, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1439492020-08-18T14:24:54Z2020-08-18T14:24:54ZSome bats find their way around like people do: why this is useful to know<figure><img src="https://images.theconversation.com/files/351121/original/file-20200804-14-z9iltl.jpg?ixlib=rb-1.1.0&rect=20%2C59%2C743%2C469&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An Egyptian Fruit Bat in flight.</span> <span class="attribution"><span class="source">Sherri and Brock Fenton</span></span></figcaption></figure><p>Flight makes bats unique among mammals and confers on them the potential to cover large distances. And yet, for most of the approximately 1,400 or so species of bats, we have little information about the extent and details of their travels. </p>
<p>Two <a href="https://science.sciencemag.org/content/369/6500/188">papers</a> <a href="https://science.sciencemag.org/content/369/6500/194">published</a> in <em>Science</em> in July 2020 have added to our understanding of how bats – specifically Egyptian Fruit bats – travel. Each paper was the work of a team of Israeli researchers who, using several kinds of technology including GPS tags, documented the movements of Egyptian Fruit bats from Israel’s Hula Valley. They showed that these bats, which weigh about 150 grams, have home ranges exceeding 60 km². They also discovered that, once they could fly, young bats took about 70 days to use home ranges as large as those of adults.</p>
<p>As an expert on bats who has published extensive research and <a href="https://books.google.co.za/books/about/Bats.html?id=4Ad-BwAAQBAJ&redir_esc=y">books</a> on these animals, I provided <a href="https://science.sciencemag.org/content/369/6500/142?rss=1">a commentary</a> in Science on these new findings. I pointed out that there was more to the papers than the extent to which these bats covered ground. Rather, the data reveal that bats used a <a href="https://www.sciencedirect.com/topics/neuroscience/cognitive-map">cognitive map</a> to navigate their home ranges. </p>
<p>This is a detailed inner ‘map’ in which information about our geographical and physical world is stored, analysed and altered as necessary. Here you might think of your own ‘home range’: how you move about in it to make the best use of your time, whether you are looking for food or to meet friends. Your cognitive map makes this second nature.</p>
<p>This important discovery demonstrates that such maps are not the exclusive domain of humans and a few other species. Documenting animals’ use of cognitive maps allows researchers to unravel the brain and sensory processes involved in navigation. It could also have positive implications for conservation, helping us to better understand the areas where these bats may travel and roost.</p>
<p>Another side to knowing about the distances covered by bats relates to public health and their association with some viral diseases that affect people. <a href="https://www.who.int/news-room/fact-sheets/detail/ebola-virus-disease">Ebola</a> is a grim example; <a href="http://scholar.google.co.za/scholar_url?url=https://www.facetsjournal.com/doi/full/10.1139/facets-2020-0028&hl=en&sa=X&scisig=AAGBfm1W57gy_SHL_zZ4zX43PQs9Vn7Bcw&nossl=1&oi=scholarr">COVID-19</a> another. <a href="https://www.idse.net/Covid19/Article/05-20/Why-Are-Bats-the-Perfect-Coronavirus-Reservoir/58486">Bats are reservoirs for SARS CoV-2</a>, which causes COVID-19. We do not yet know how this virus moves from bats to people. Learning more about how bats operate can only benefit us. </p>
<h2>Diverse and quite different</h2>
<p>Bats are diverse, distinctive, and quite different from other mammals. For example, they bear large young (about 25% of the mother’s body mass), and many live a long time – about 20 years in the wild. Most bats orient by biosonar or echolocation, allowing them to ‘see’ in the dark. </p>
<p>Africa has <a href="https://www.awf.org/wildlife-conservation/bat#:%7E:text=Over%20200%20species%20of%20African,percent%20of%20the%20world's%20bats.&text=Varies%20by%20species%20%E2%80%94%20the%20largest,840%20mm%20(33%20inches).">more than 200 species</a> of bats, ranging in body mass from about 3g to around 300g. African bats play different roles in ecosystems, but most eat mainly insects and other arthropods. Some African species eat fruit and disperse seeds, while others visit flowers and are important as pollinators. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/351122/original/file-20200804-20-1s7ttzk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/351122/original/file-20200804-20-1s7ttzk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=273&fit=crop&dpr=1 600w, https://images.theconversation.com/files/351122/original/file-20200804-20-1s7ttzk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=273&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/351122/original/file-20200804-20-1s7ttzk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=273&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/351122/original/file-20200804-20-1s7ttzk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=343&fit=crop&dpr=1 754w, https://images.theconversation.com/files/351122/original/file-20200804-20-1s7ttzk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=343&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/351122/original/file-20200804-20-1s7ttzk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=343&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A bushveld bat emerging from a cave.</span>
<span class="attribution"><span class="source">Sherri and Brock Fenton</span></span>
</figcaption>
</figure>
<p>As their name implies, the Egyptian Fruit bat that was the subject of these two studies occurs mainly in Africa, from Cape Town northwards, and into some areas in the Middle East. They eat fruit and are common zoo animals, well known to many people well beyond Africa. </p>
<p>Bats are mainly nocturnal and their survival means having a safe place to spend the day. They roost in a wide variety of places, from underground hollows (caves and mines), to hollows in trees and in buildings. Some roost in foliage; others out in plain sight. Some roosts contain thousands of bats, but many others shelter only a few individuals. </p>
<p>In different parts of the world, banding studies – in which bands are used to mark and identify the animals – have revealed that individual bats return to the same roosts year after year, over decades. One banded Brandt’s myotis returned to the same site each year for <a href="https://pubmed.ncbi.nlm.nih.gov/16339320/">over 40 years</a>. We now know that many bats use a variety of roosts and this repertoire provides appropriate shelter and access to other group members. Use of cognitive maps explains this behaviour. Detailed knowledge of their home ranges, whether places to roost or to find food, are vital to the survival of bats – whether of individuals or species. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/353047/original/file-20200816-20-1rr0j83.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/353047/original/file-20200816-20-1rr0j83.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=702&fit=crop&dpr=1 600w, https://images.theconversation.com/files/353047/original/file-20200816-20-1rr0j83.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=702&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/353047/original/file-20200816-20-1rr0j83.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=702&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/353047/original/file-20200816-20-1rr0j83.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=882&fit=crop&dpr=1 754w, https://images.theconversation.com/files/353047/original/file-20200816-20-1rr0j83.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=882&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/353047/original/file-20200816-20-1rr0j83.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=882&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A mother epauletted fruit bat with her almost independent young. They occur widely in African savannahs.</span>
<span class="attribution"><span class="source">Sherri and Brock Fenton</span></span>
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</figure>
<p>Some bats lead very social lives and being with group members can be important to them. Contact with others allows many bats to save energy; they huddle to keep warm. It can also improve their chances for reproductive success. Such detailed knowledge is central to our lives as well – and, as with bats, involves cognitive maps. We know where to find shelter, food, our friends. This new research shows that bats know the same things. </p>
<h2>Why it matters</h2>
<p>Bats’ use of cognitive maps raises interesting questions about their conservation. Bats’ small size, low reproductive output, and longevity make them vulnerable. Destruction of roosts and foraging areas puts many bats at risk. Too often, the situation is exacerbated by bats’ negative image. </p>
<p>Effective conservation plans mean protecting bats’ home ranges. Most lists of bats occurring in an area, for example a national park, indicate where species have been reported, and perhaps the locations of some roosts.</p>
<p>To effectively protect areas vital to a species, we also must know how far they range, as well as why and how they use different features and areas. Knowing that bats likely have cognitive maps makes it easier for us to appreciate the areas they cover and to plan accordingly.</p>
<p>There are possible benefits for public health, too. Almost everywhere in the world, bats coexist with people. Learning more about how they operate – for example how they <a href="https://elifesciences.org/articles/48401">neutralise viruses</a> that are potentially fatal to us – can benefit us.</p><img src="https://counter.theconversation.com/content/143949/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Melville (Brock) Fenton does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>This important discovery demonstrates that cognitive maps are not the exclusive domain of humans and a few other species.Melville (Brock) Fenton, Emeritus Professor of Biology, Western UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/771152017-05-12T12:00:25Z2017-05-12T12:00:25ZFive amazing ultrasound inventions set to change the world (and not a pregnancy scan in sight)<figure><img src="https://images.theconversation.com/files/169122/original/file-20170512-3692-1j39iqt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ultrasonic "tractor beam"</span> <span class="attribution"><span class="source">Asier Marzo, Bruce Drinkwater, Sriram Subramanian</span></span></figcaption></figure><p>Ultrasound can do a whole lot more than create images of unborn babies. Since it first became a near-indispensable medical tool <a href="http://www.genesis-ultrasound.com/venous-ultrasound.html">in the 1930s</a>, technology that produces sound waves so high-pitched that humans can’t hear them has found use in almost every branch of industry. The vibrations it creates can kill bacteria, weld plastics and even help to mature brandies in a matter of <a href="http://www.ibtimes.com/how-age-liquor-ultrasound-ages-brandy-just-days-compared-years-study-shows-2490093">days rather than years</a>.</p>
<p>Today, ultrasound is finding its way into even more applications, powering inventions that have the potential to make huge changes in their fields. Here are just a few of them:</p>
<h2>1. Truly hands-free phones</h2>
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<p>We are on the brink of a real contactless alternative to touch-screen technology. Devices like the Microsoft Kinect can detect where you hands are and use that information as instructions. But placing your hands in exactly the right place to give the instructions you want to is still tricky enough to prevent this kind of gesture-based control system from being used more widely.</p>
<p>One company is using ultrasound to effectively create <a href="https://www.theguardian.com/business/2015/oct/25/the-innovators-invisible-buttons-ultrahaptics">invisible buttons in the air</a> that you can feel. An array of ultrasound transmitters produces and shapes sound waves to create small areas of force sensations on the skin in a specific location. So instead of waving your hand around and hoping it’s in the right place, you know instantly when you’ve activated the gesture recognition.</p>
<p>This has the potential to make everyday devices such as smartphones completely waterproof, contactless and effectively aware of the surrounding environment. The technology can also be <a href="https://venturebeat.com/2016/11/07/ultrahaptics-uses-ultrasound-so-you-can-feel-things-in-vr/">combined with virtual reality</a> systems to enable you to feel your artificially generated surroundings, which would bring a new dimension to video games and entertainment.</p>
<p><a href="http://bgr.com/2017/03/03/iphone-8-rumors-touch-id-sensor/">There are rumours</a> that the next generation of smartphones will use ultrasonic fingerprint recognition so you don’t even need to touch your phone to unlock it. These phones could even incorporate ultrasound for <a href="https://www.slashgear.com/ubeam-publicly-unveils-its-ultrasonic-wave-based-wireless-charging-05473955/">wireless charging</a>, where ultrasound energy could be converted to electrical energy within the phone. This energy would be projected from a transmit unit stored, for example, on the wall in your house.</p>
<h2>2. Acoustic holograms</h2>
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<p>Ultrasound has long been used to create two-dimensional images of the body for doctors to study. But a very recent development that is likely to feature prominently in healthcare in the future is the <a href="http://www.nature.com/nature/journal/v537/n7621/full/nature19755.html">ultrasound acoustic hologram</a>.</p>
<p>In this technique, ultrasound is used to move micro-particles in a particular medium to form a desired image. For example, projecting sound waves through a specially-designed patterned plate into water containing plastic particles forces them into a particular alignment. Researchers think this kind of acoustic holography could be used to improve medical imaging but also to better focus ultrasound treatments.</p>
<h2>3. Glasses for blind people</h2>
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<p>Another potential medical application of ultrasound is to enable blind people to “see” in a similar way to how bats do using the principle of echolocation. Rather than detecting reflected light waves to see objects, bats send out ultrasound waves and use the reflected sound to work out where things are. These echoes can provide information about the size and location of that object.</p>
<p>Researchers in California have created an <a href="http://www.popsci.com/ultrasonic-helmet-lets-anyone-see-bat">ultrasonic helmet</a> that sends out similar ultrasound waves. It then converts the reflected signals into audible sounds that the human brain can learn to process into a detailed mental image of the environment. In time, this technology could become more practical and portable, perhaps even one day incorporated into specially designed glasses.</p>
<h2>4. Tractor beams</h2>
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<p>Given enough power, it is possible to <a href="https://www.nature.com/articles/ncomms9661">ultrasonically levitate</a> objects just with sound waves, and move them in different directions, effectively <a href="http://www.smithsonianmag.com/science-nature/acoustic-tractor-beam-can-levitate-small-objects-sound-180957060/">like a science fiction tractor beam</a>. Researchers from the University of Bristol have shown that by controlling and focusing sound waves from an array of ultrasound sources can create enough force to lift a bead-sized object off the ground.</p>
<p>Lifting larger objects, such as a human, would require very high power levels, and it is not fully understood how damaging the acoustic forces would be to a person. But the technology has the potential to revolutionise a range of <a href="http://news.mit.edu/2015/ultrasound-drug-delivery-inflammatory-bowel-disease-1021">medical applications</a>. For example it could be used to move drugs around the body to get them to their target cells.</p>
<h2>5. Martian scanners</h2>
<p>Ultrasound technology is already being investigated as an exploration tool. At high power, ultrasonic vibrations can be used to efficiently compact material, like a kind of drill hammering its way through. This has been proposed for use in the search for <a href="http://www.ogic.co.uk/badger-explorer/">underground oil and gas deposits</a>. Ultrasonic echolocation can also be used as a type of sensor to help <a href="http://newatlas.com/sensefly-exom-quadcopter-drone/34650/">aerial drones</a> avoid obstacles so they can be sent into dangerous and difficult-to-reach locations.</p>
<p>But exploration is not limited to Planet Earth. If humans are ever to visit Mars, we’ll need new ways of analysing the Martian environment. Because of the low gravity on Mars, conventional drills wouldn’t be able to press down with as much force, so researchers are looking <a href="http://www.gla.ac.uk/research/infocus/themes/space/projects/ultrasonicdrilltoolsforplanetaryexploration/">at how ultrasonic devices</a> could be used to collect samples instead.</p><img src="https://counter.theconversation.com/content/77115/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Feeney receives funding from the Engineering and Physical Sciences Research Council (EPSRC). </span></em></p>From acoustic holograms to tractor beams.Andrew Feeney, Research Fellow in Ultrasonics, University of WarwickLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/646722016-09-02T03:55:46Z2016-09-02T03:55:46ZIt’s time to speak up about noise pollution in the oceans<figure><img src="https://images.theconversation.com/files/136378/original/image-20160902-1048-rjguta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sperm whales, like many other species, use echolocation which can be hampered by noise.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3AMother_and_baby_sperm_whale.jpg">Gabriel Barathieu/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Ask most people about pollution, and they will think of rubbish, plastic, oil, smog, and chemicals. After some thought, most folks might also suggest noise pollution. </p>
<p>We’re all familiar with noise around us, and we know it can become a problem – especially if you live near an airport, train station, highway, construction site, or DIY-enthusiast neighbour.</p>
<p>But most people don’t think that noise is a problem under water. If you’ve read Jules Verne’s <a href="https://en.wikipedia.org/wiki/Twenty_Thousand_Leagues_Under_the_Sea">Twenty Thousand Leagues Under the Sea</a> you might imagine that, maelstroms excepted, life is pretty quiet in the ocean. Far from it.</p>
<p>When we put a hydrophone (essentially a waterproof microphone) into the water, no matter where in the world’s oceans, it’s never quiet. We hear wind blowing overhead and rain dropping onto the ocean surface – even from <a href="http://www.sciencedirect.com/science/article/pii/S0079661115001123">hundreds of metres deep</a>. In Australian waters we can also detect the far-off rumbles of earthquakes and the creaking of <a href="https://youtu.be/E3llmXMoPvU">Antarctic ice</a> thousands of kilometres away.</p>
<h2>Wet and noisy</h2>
<p>Water is much denser than air, so its molecules are packed tighter together. This means that sound (which relies on molecules vibrating and pushing against one another) propagates much <a href="http://www.engineeringtoolbox.com/sound-speed-water-d_598.html">further and faster</a> under water than in air.</p>
<p>This also applies to human-produced sound. Under water we can hear <a href="https://www.youtube.com/watch?v=6MnwR4SYhJA">boats</a> and <a href="https://www.youtube.com/watch?v=S8Jd4wnbX_Q">ships</a> and even <a href="https://www.youtube.com/watch?v=cC26lPu4agM">aeroplanes</a>. Large vessels in deep water can be detected <a href="http://www.sciencedirect.com/science/article/pii/S0079661115001123">tens of kilometres away</a>. We can be far offshore doing fieldwork, the only people around, with nothing in sight but water in any direction. Yet when we switch the engines off and put a hydrophone into the water, we hear ship noise. Sometimes, whole minutes later, the vessel we heard might appear on the horizon.</p>
<p>Seafarers have known about another source of sound for thousands of years: marine life. Many animals produce sound, from the tiniest <a href="https://www.youtube.com/watch?v=SoyT81_s3HM">shrimp</a> to the biggest <a href="https://www.youtube.com/watch?v=QUIoO0u5hR8">whales</a>. Many <a href="https://youtu.be/m7KLR1PRHj4">fish</a> even communicate acoustically under water – during the mating season, the boys start calling. Whales do it, too.</p>
<p>Light doesn’t reach far under water. Near the surface, in clear water, you might be able to peer a few metres, but in the inky depths you can’t see at all. So many marine animals have evolved to “see with sound”, using acoustics for navigation, for detecting predators and prey, and for communicating with other members of their species. </p>
<p>The thing is that man-made sound can interfere with these behaviours.</p>
<p>The <a href="http://link.springer.com/chapter/10.1007/978-1-4419-7311-5_3">effects of noise on marine animals</a> are similar to those on us. If you’ve ever been left with ringing ears after a rock concert, you’ll know that loud noise can temporarily affect your hearing or even damage it permanently. </p>
<p>Noise interferes with <a href="http://www.sciencedirect.com/science/article/pii/S0025326X15302125">communication</a>, often masking it. Can you talk above the background noise in a busy pub? Long-term exposure to noise can cause <a href="http://jeb.biologists.org/content/207/3/427">stress</a> and health issues — in humans and animals alike. </p>
<p>Excessive noise can change marine creatures’ habits, too. Like a person who decides to move house rather than live next door to a new airport, animals might choose to <a href="http://icesjms.oxfordjournals.org/content/59/1/71">desert their habitat</a> if things get too noisy. The question is whether they can find an equally acceptable habitat elsewhere.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/136376/original/image-20160902-1048-u7f8rf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/136376/original/image-20160902-1048-u7f8rf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/136376/original/image-20160902-1048-u7f8rf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136376/original/image-20160902-1048-u7f8rf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136376/original/image-20160902-1048-u7f8rf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136376/original/image-20160902-1048-u7f8rf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136376/original/image-20160902-1048-u7f8rf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136376/original/image-20160902-1048-u7f8rf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pile-driving is noisy work.</span>
<span class="attribution"><span class="source">Christine Erbe</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>There is a lot more research still to be done in this field. Can we predict what noises and vibrations might be released into the marine environment by new machinery or ships? How does sound propagate through different ocean environments? What are the long-term effects on marine animal populations?</p>
<p>One positive is that even though noise pollution travels very fast and very far through the ocean, the moment you switch off the source, the noise is gone. This is very much unlike plastic or chemical pollution, and gives us hope that noise pollution can be successfully managed.</p>
<p>We all need energy, some of which comes from oil and gas; most of our consumer goods are shipped across the seas on container vessels; and many of us enjoy eating seafood caught by noisy fishing boats, some of which <a href="https://en.wikipedia.org/wiki/Blast_fishing">even use dynamite to catch fish</a>. We want to protect our borders, making naval operations a necessity. Then there’s the ever growing industry of marine tourism, much of it aboard ever-bigger cruise ships which need large ports in which to berth. </p>
<p>There are a lot of stakeholders in the marine environment, and all speak a different language, all make different claims, and all make noise. Knowing precisely how much noise they make, and how it affects marine life, will help to ensure our oceans and their resources last well into the future.</p>
<hr>
<p><em>September 3-11 is <a href="http://www.aaee.org.au/seaweek-2016/">SeaWeek 2016</a>, the Australian Association for Environmental Education Marine Educators’ national public awareness campaign.</em></p><img src="https://counter.theconversation.com/content/64672/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christine Erbe receives funding from offshore petroleum companies, defence departments, environmental groups. </span></em></p>We tend to think of the oceans as quiet, when in fact they’re anything but. Noise is the “forgotten pollutant”, but the good news is that unlike many other pollutants it can be switched off if we try.Christine Erbe, Director, Centre for Marine Science & Technology, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.