tag:theconversation.com,2011:/id/topics/chameleon-5419/articlesChameleon – The Conversation2023-10-17T15:29:28Ztag:theconversation.com,2011:article/2123082023-10-17T15:29:28Z2023-10-17T15:29:28ZHow animal traits have shaped the journey of species across the globe<p>The devastating <a href="https://www.ngdc.noaa.gov/hazel/view/hazards/tsunami/event-more-info/5413">tsunami</a> that hit Japan in March 2011 set off a series of events which have long fascinated scientists like me. It was so powerful that it caused 5 million tonnes of debris to <a href="https://marinedebris.noaa.gov/japan-tsunami-marine-debris/monitoring-tsunami-debris-north-american-shorelines">wash</a> into the Pacific – 1.5 million tonnes remained afloat and started drifting with the currents. </p>
<p>One year later, and half a world away, debris began washing ashore on the west coast of North America. More than 280 Japanese coastal species such as mussels, barnacles and even some species of fish, had <a href="https://www.science.org/doi/full/10.1126/science.aao1498?casa_token=YwHfCNElf14AAAAA:zJj4eY3uUm2_m4ZH5YzIO6ecvSWdVa_53yZk0ycnxm1Ga3bPLTl5Z6hCbUhvsmA4d0KSPHFPKz84nQ">hitched a ride</a> on the debris and made an incredible journey across the ocean. These species were still alive and had the potential to establish new populations. </p>
<p>How animals cross major barriers, such as oceans and mountain ranges, to shape Earth’s biodiversity is an intriguing topic. And a new <a href="https://www.nature.com/articles/s41559-023-02150-5">study</a> by my collaborators and I has shed light on this process, revealing how animal characteristics such as body size and life history can influence their spread across the globe.</p>
<p>We know that such dispersal events occur in terrestrial species as well. For instance, at least 15 green iguanas <a href="https://www.nature.com/articles/26886">journeyed</a> more than 200km (124 miles) from Guadeloupe to Anguilla in the Caribbean in 1995. They arrived on a mat of logs and trees (likely uprooted through a hurricane), some of which were more than 9 metres (20 feet) long. </p>
<h2>The role of animal characteristics in dispersal</h2>
<p>When animals move across major barriers it can have a big impact on both the new and old locations. For example, an invasive species can arrive in a new area and compete with native species for resources. However, those consequences can be even greater over longer periods of time.</p>
<p>The movement of monkeys from Africa to South America around 35 million years ago led to the evolution of more than 90 species of <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev-anthro-102116-041510?casa_token=CZtEoQ5Z9bMAAAAA%3AX9JrgVyGxxegDXgVTUPNHZboMldBec1egagn5S4pLwx4yudreF4L6Q6zG4jUeB9tMxJEIy4q67iX&journalCode=anthro">New World monkeys</a>, including tamarins, capuchins and spider monkeys. And a few chameleons rafting on vegetation from Africa to Madagascar is why we find half of all living <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2013.0184">chameleon</a> species there today.</p>
<p>These events were long thought to be determined by chance – the coincidence of some chameleons sitting on the right tree at the right time. However, <a href="https://www.jstor.org/stable/pdf/24529638.pdf?casa_token=NyxiUsFXod0AAAAA:9aBvrCPO0om98AjWOfs482QWf5eQxRUwKt95p4S3trPy1CQ2CM4K0AJeMBtsNKwKST8ILswcwdjQBRq8ZpdR5-3KL3gOn9uYZHOjzDdPyTm4R3Dom1o">some scientists</a> have suggested there might be more to it. They hypothesised there could be more general patterns in the animals that reach their destination successfully, related to certain characteristics.</p>
<p>Could body size affect how far a species can travel? Animals with more fat reserves may be able to travel longer distances. Or could it be how a species reproduces and survives? For example, animals that lay many eggs or mature early may be more likely to establish a new population in a new place.</p>
<p>But despite a vigorous theoretical debate, the options to test these hypotheses were limited because such dispersal events are rare. Also, the right statistical tools were not available until recently.</p>
<p>Thanks to the recent development of new <a href="https://academic.oup.com/sysbio/article/69/1/61/5490843">biogeographical models</a> and the great availability of data, we can now try to answer questions about how tetrapod species (amphibians, reptiles, birds and mammals) have moved around the globe over the past 300 million years and whether successful species share any common characteristics.</p>
<p>These models allow us to estimate the movements of species’ ancestors while also considering their characteristics. We used these models to study 7,009 species belonging to 56 groups of tetrapods.</p>
<h2>What we found</h2>
<p>For 91% of the animal groups we studied, models that included species characteristics were better supported than models that didn’t. This means that body size and life history are closely linked to how successful a species is at moving to and establishing itself in a new location.</p>
<p>Animals with large bodies and fast life histories (breeding early and often, like water voles) generally dispersed more successfully, as expected. However, there were some exceptions to this rule. In some groups, smaller animals or animals with average traits had higher dispersal rates.</p>
<p>For example, small hummingbirds dispersed better than larger ones, and poison dart frogs with intermediate life histories dispersed better than those with very fast or very slow life histories.</p>
<p>We investigated this variation further and found that the relationship between body size and movement depended on the average size and life history of the group. Our results show that the links between characteristics and dispersal success depend on both body size and life history, and that these cannot be considered separately. </p>
<p>Groups in which small size was an advantage were often already made up of small species (making the dispersal-prone species even smaller), and these species also had fast life histories. We found this to be true for the rodent families <a href="https://www.britannica.com/animal/Muridae"><em>Muridae</em></a> and <a href="https://nhpbs.org/wild/cricetidae.asp"><em>Cricetidae</em></a>. </p>
<p>But groups in which dispersers had intermediate body sizes generally had slow life histories (meaning they had low reproductive output but long lifespans). This means the combination of small body size and slow life history is very unlikely to be an advantage for dispersal across major barriers such as oceans.</p>
<h2>It’s not just chance</h2>
<p>It is amazing to think that rare dispersal events, which can lead to the rise of many new species, are not completely random. Instead, the intrinsic characteristics of species can shape the histories of entire groups of animals, even though chance still may play an important role.</p>
<p>At the same time, two of the most important <a href="https://zenodo.org/record/3553579">environmental challenges</a> of our time are related to movement across major barriers: biological invasions and species’ responses to climate change. On a planet facing rapid changes, understanding how animals move across barriers is therefore crucial.</p><img src="https://counter.theconversation.com/content/212308/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>While working on this study, Sarah-Sophie Weil was affiliated with Université Grenoble Alpes (France) and Swansea University (Wales, UK) who supported her through Initiative d’excellence (IDEX) International Strategic Partnership and Swansea University Strategic Partner Research (SUSPR) scholarships.</span></em></p>New research looks at how different species have managed to cross geographic barriers throughout history and whether their individual traits played a crucial role in these journeys.Sarah-Sophie Weil, PhD candidate, Swansea UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1824272022-05-11T19:55:02Z2022-05-11T19:55:02ZTug of war between survival and reproductive fitness: how chameleons become brighter without predators around<figure><img src="https://images.theconversation.com/files/462190/original/file-20220510-22-8t3is2.jpg?ixlib=rb-1.1.0&rect=56%2C0%2C2471%2C921&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Martin Whiting</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Invasive species offer a rare research opportunity, as they often colonise new environments very different to their native habitat. One such species is the Jackson’s three-horned chameleon (<em>Triocerus j. xantholophus</em>), which was accidentally introduced to the Hawaiian Islands in the 1970s. </p>
<p>Our study, <a href="https://doi.org/10.1126/sciadv.abn2415">published today</a> in Science Advances, shows Hawaiian chameleons display much brighter social signals than individuals from their native habitat range in East Africa – and could represent an example of rapid evolution. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461690/original/file-20220506-26-f6phtq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/461690/original/file-20220506-26-f6phtq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461690/original/file-20220506-26-f6phtq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=569&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461690/original/file-20220506-26-f6phtq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=569&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461690/original/file-20220506-26-f6phtq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=569&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461690/original/file-20220506-26-f6phtq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=715&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461690/original/file-20220506-26-f6phtq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=715&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461690/original/file-20220506-26-f6phtq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=715&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 male Jackson’s three-horned chameleon (above) courting a female (below) in Kenya.</span>
<span class="attribution"><span class="source">Martin Whiting.</span></span>
</figcaption>
</figure>
<h2>A long way from home</h2>
<p>In 1972, about 36 Jackson’s chameleons made their way from their native Kenya to the Hawaiian island of Oahu, destined for the pet trade.</p>
<p>The chameleons were a little worse for wear by the time they arrived in Hawaii, following a long and taxing journey that would have begun days before they were loaded onto the plane in Nairobi.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461687/original/file-20220506-22-ipiyi3.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/461687/original/file-20220506-22-ipiyi3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461687/original/file-20220506-22-ipiyi3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=367&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461687/original/file-20220506-22-ipiyi3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=367&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461687/original/file-20220506-22-ipiyi3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=367&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461687/original/file-20220506-22-ipiyi3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=462&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461687/original/file-20220506-22-ipiyi3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=462&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461687/original/file-20220506-22-ipiyi3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=462&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Invasive chameleons have made it to the Hawaiian islands – the world’s most isolated island archipelago.</span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
</figcaption>
</figure>
<p><a href="https://chicagoherp.org/wp-content/uploads/bsk-pdf-manager/2019/12/263.pdf">The story goes</a> that an Oahu pet shop owner, Robin Ventura, opened the crate in his garden to give them fresh air and an opportunity to recover. Presumably, he underestimated the speed with which chameleons can move (and recover) – and they quickly dispersed into the surrounding area.</p>
<p>This founding population represented an accidental invasion, and subsequently became an unplanned experiment in evolution. What happens when an animal with colourful social displays – from a population with lots of bird and snake predators – is introduced to an island virtually free of predators? </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-do-chameleons-and-other-creatures-change-colour-13842">How do chameleons and other creatures change colour?</a>
</strong>
</em>
</p>
<hr>
<h2>Evolution in action?</h2>
<p>We predicted Hawaiian chameleons, as a result of being relatively free from predation, would have more elaborate or brighter displays than their Kenyan counterparts. We also predicted they would be more conspicuous when viewed by their East African predators, such as birds and snakes.</p>
<p>In the animal kingdom, bright or colourful displays can attract the attention of sharp-eyed predators. This reduces an individual animal’s likelihood of survival and, by extension, its reproductive fitness (or the number of genes it passes on to future generations). </p>
<p>When survival is threatened, <a href="https://en.wikipedia.org/wiki/Natural_selection">natural selection</a> acts as a brake and halts the further elaboration of colour, or shifts bright colours to areas of the body less visible to predators. </p>
<p>For instance, many lizard species have bright colours concealed on their undersides or throats. In South Africa, male Augrabies flat lizards will signal to rival males by raising their underside and exposing the throat, which is puffed out.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461692/original/file-20220506-1367-w6uifv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/461692/original/file-20220506-1367-w6uifv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461692/original/file-20220506-1367-w6uifv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461692/original/file-20220506-1367-w6uifv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461692/original/file-20220506-1367-w6uifv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461692/original/file-20220506-1367-w6uifv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=562&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461692/original/file-20220506-1367-w6uifv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=562&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461692/original/file-20220506-1367-w6uifv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=562&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many lizard species, such as this Augrabies flat lizard, have bright colours on body parts that are less visible to predators such as birds.</span>
<span class="attribution"><span class="source">Martin Whiting</span></span>
</figcaption>
</figure>
<p>On the other hand, conspicuous displays may also increase fitness. For example, brighter or more colourful males may gain greater access to females, either by winning contests with rival males, or simply appearing more attractive to females.</p>
<p>This tug of war between survival and fitness is well documented in species with fixed or seasonally dependent colouration. For instance, <a href="https://theguppyproject.weebly.com/">guppies</a> become less colourful when dangerous predators share their streams. However, it’s less understood in animals with dynamic colour change such as chameleons. </p>
<p>Although we have a good understanding of <a href="https://theconversation.com/how-do-chameleons-and-other-creatures-change-colour-13842">how chameleons change colour</a>, we don’t know if they modulate their displays when there are more predators in their environment. It may also be that natural selection prevents them from producing colour signals that are colourful or bright beyond a certain threshold.</p>
<p>To test our predictions, we travelled to Kenya and Hawaii to study colour change in wild chameleons.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-G2WYnb265I?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">In rivalling male chameleons, dominance is signalled by turning from green to lemon-yellow. In this clip, two males are evenly matched and both signal their dominance. When the contest is settled, the winner remains lemon-yellow a while longer while the subordinate turns brown.</span></figcaption>
</figure>
<h2>Vibrant test subjects</h2>
<p>Chameleons are great study subjects because they have a very strong stimulus response. You can pop them on a branch away from their usual haunts and present them with a fake predator or another chameleon, and they will devote all their attention to the stimulus while completely ignoring you!</p>
<p>We presented each male chameleon with a rival male, a female, a model bird predator and a model snake predator - each in a one-on-one interaction. During the presentations we measured their colour using an optic spectrometer. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461693/original/file-20220506-1371-szia9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/461693/original/file-20220506-1371-szia9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461693/original/file-20220506-1371-szia9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=319&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461693/original/file-20220506-1371-szia9x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=319&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461693/original/file-20220506-1371-szia9x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=319&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461693/original/file-20220506-1371-szia9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=401&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461693/original/file-20220506-1371-szia9x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=401&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461693/original/file-20220506-1371-szia9x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=401&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chameleons were exposed to a model snake (pictured: African boomslang) and bird (pictured: African cuckoo-hawk) predators.</span>
<span class="attribution"><span class="source">Martin Whiting</span></span>
</figcaption>
</figure>
<p>This instrument allows us to quantify two metrics of colour: chromatic contrast (essentially how colourful they are) and luminance contrast (how bright they are). We could then estimate how detectable a displaying chameleon would be to an observer – be it another chameleon, or a bird or snake predator.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461696/original/file-20220506-18-isgb96.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/461696/original/file-20220506-18-isgb96.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461696/original/file-20220506-18-isgb96.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=362&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461696/original/file-20220506-18-isgb96.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=362&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461696/original/file-20220506-18-isgb96.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=362&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461696/original/file-20220506-18-isgb96.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=455&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461696/original/file-20220506-18-isgb96.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=455&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461696/original/file-20220506-18-isgb96.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=455&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chameleons lock horns during fights for dominance.</span>
<span class="attribution"><span class="source">Devi Stuart-Fox</span></span>
</figcaption>
</figure>
<p>We also measured the leafy vegetation that forms the backdrop against which a chameleon signals. This way we could estimate how detectable a displaying chameleon would be against a particular background. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461697/original/file-20220506-1367-gl64c3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/461697/original/file-20220506-1367-gl64c3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461697/original/file-20220506-1367-gl64c3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461697/original/file-20220506-1367-gl64c3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461697/original/file-20220506-1367-gl64c3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461697/original/file-20220506-1367-gl64c3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461697/original/file-20220506-1367-gl64c3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461697/original/file-20220506-1367-gl64c3.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">A male Jackson’s three-horned chameleon from Hawaii, showing subordinate colours.</span>
<span class="attribution"><span class="source">Martin Whiting</span></span>
</figcaption>
</figure>
<h2>An exciting example of rapid change</h2>
<p>The results were particularly exciting and exceeded our expectations. We found Hawaiian chameleons had much brighter displays than Kenyan chameleons during male contests and when courting females. They were also more conspicuous against their Hawaiian background than a Kenyan background. </p>
<p>This is consistent with what scientists term “local adaptation”. This is the idea that signals will be fine-tuned to be more detectable in the environment in which they are used. </p>
<p>For Hawaiian chameleons, one unintended consequence of being brighter was they were also more detectable to their native predators.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/461691/original/file-20220506-21-fxggne.png?ixlib=rb-1.1.0&rect=70%2C542%2C2279%2C2257&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/461691/original/file-20220506-21-fxggne.png?ixlib=rb-1.1.0&rect=70%2C542%2C2279%2C2257&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/461691/original/file-20220506-21-fxggne.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461691/original/file-20220506-21-fxggne.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461691/original/file-20220506-21-fxggne.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461691/original/file-20220506-21-fxggne.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461691/original/file-20220506-21-fxggne.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461691/original/file-20220506-21-fxggne.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"></a>
<figcaption>
<span class="caption">A male Jackson’s three-horned chameleon living wild on Oahu, Hawaii.</span>
<span class="attribution"><span class="source">Brenden S. Holland</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Interestingly, this effect was more pronounced when facing birds compared to snakes – probably because snakes have poorer colour discrimination than birds. Finally, Hawaiian chameleons also had a greater capacity to change colour than Kenyan chameleons - they could do so over a greater range.</p>
<p>We can’t be completely sure brighter signals in Hawaiian chameleons represents rapid evolution. It’s also possible this degree of colour change is due to <a href="https://en.wikipedia.org/wiki/Phenotypic_plasticity">plasticity</a>, which is when an animal changes to a different state due to prevailing environmental conditions. </p>
<p>Nevertheless, plasticity itself can evolve – and colour change in chameleons may be a combination of both evolutionary change and plasticity. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461698/original/file-20220506-21738-2511zc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/461698/original/file-20220506-21738-2511zc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461698/original/file-20220506-21738-2511zc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=271&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461698/original/file-20220506-21738-2511zc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=271&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461698/original/file-20220506-21738-2511zc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=271&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461698/original/file-20220506-21738-2511zc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=340&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461698/original/file-20220506-21738-2511zc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=340&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461698/original/file-20220506-21738-2511zc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=340&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 male Jackson’s three-horned chameleon from Kenya in full display colour.</span>
<span class="attribution"><span class="source">Martin Whiting</span></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/182427/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Whiting works for Macquarie University. He receives funding from the Australian Research Council.</span></em></p>Researchers wanted to understand what happens when chameleons – animals that display dynamic colour change – find themselves in an environment without their natural predators.Martin Whiting, Professor of Animal Behaviour, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1576332021-03-28T08:49:48Z2021-03-28T08:49:48ZWhat Madagascar’s amazing mini creatures tell us about evolution<figure><img src="https://images.theconversation.com/files/392048/original/file-20210327-21-1lcbjx6.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Brookesia tedi, described in 2019, is one of the smallest chameleons, and indeed one of the smallest amniote vertebrates, on earth. </span> <span class="attribution"><span class="source">Mark D. Scherz</span></span></figcaption></figure><p><em>Madagascar has many “mini” creatures. These include a recently discovered group of miniaturised frogs as well as the discovery earlier this year of the <a href="https://www.bbc.com/news/world-africa-55945948">smallest reptile on earth</a> – the Brookesia nana, or nano-chameleon, which is the size of a paperclip. Moina Spooner, from The Conversation Africa, asked Dr Mark D. Scherz, an amphibian and reptile specialist who focuses on Madagascar, to explain what causes these animals to miniaturise.</em></p>
<h2>Which miniaturised species have been discovered recently?</h2>
<p>Madagascar is famous for its small animals; the mouse lemurs, the smallest primates on earth, for instance, are widely known. There’s also growing awareness that Madagascar is home to a variety of other uniquely miniaturised animals, especially chameleons and frogs. In those groups, researchers have discovered large numbers of tiny species in recent years. </p>
<p>In 2017, researchers described 26 species of <em>Stumpffia</em> – a group of frogs – the smallest of which is not even 1cm long at adult body size. It is one of the smallest frogs in the world. </p>
<figure class="align-center ">
<img alt="Frog on a leaf with a human finger next to it to show relative size" src="https://images.theconversation.com/files/391646/original/file-20210325-15-1lsr12z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/391646/original/file-20210325-15-1lsr12z.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=454&fit=crop&dpr=1 600w, https://images.theconversation.com/files/391646/original/file-20210325-15-1lsr12z.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=454&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/391646/original/file-20210325-15-1lsr12z.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=454&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/391646/original/file-20210325-15-1lsr12z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=571&fit=crop&dpr=1 754w, https://images.theconversation.com/files/391646/original/file-20210325-15-1lsr12z.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=571&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/391646/original/file-20210325-15-1lsr12z.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=571&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Stumpffia yanniki, a moderately small narrow-mouthed frog species from northern Madagascar, described in 2017.</span>
<span class="attribution"><span class="source">Mark D. Scherz</span></span>
</figcaption>
</figure>
<p>Then, in 2019, my colleagues and I showed that several different groups of cophyline microhylids – a group of narrow-mouthed frogs that are only found in Madagascar – have become miniaturised independently. One group of these was an entirely new genus. We gave them the fitting name “<em>Mini</em>”, with the three species <em>Mini mum</em>, <em>Mini scule</em>, and <em>Mini ature</em>. </p>
<hr>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/meet-the-mini-frogs-of-madagascar-the-new-species-weve-discovered-113946">Meet the mini frogs of Madagascar -- the new species we've discovered</a>
</strong>
</em>
</p>
<hr>
<p>We have also found some new tiny chameleons. In 2019, we described <a href="https://zse.pensoft.net/article/32818/"><em>Brookesia tedi</em></a>, a chameleon that reaches a total length of just 32mm. And then in early 2021, we described <a href="https://www.nature.com/articles/s41598-020-80955-1"><em>Brookesia nana</em></a>, the smallest chameleon, which has adult males of just 21.6mm total length, and females 28.9mm.</p>
<h2>Why have they evolved to be so small?</h2>
<p>There are probably many different reasons why these animals have evolved to be so small. For instance, it might be possible for them to exploit new resources that weren’t previously available to them. This may be new food sources, or exploring the space between leaves and tree roots that is inaccessible to larger animals. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/391413/original/file-20210324-23-pwx674.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/391413/original/file-20210324-23-pwx674.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/391413/original/file-20210324-23-pwx674.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/391413/original/file-20210324-23-pwx674.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/391413/original/file-20210324-23-pwx674.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/391413/original/file-20210324-23-pwx674.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/391413/original/file-20210324-23-pwx674.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">Stumpffia madagascariensis is a tiny leaf-litter dwelling frog from northern Madagascar.</span>
<span class="attribution"><span class="source">Mark D. Scherz</span></span>
</figcaption>
</figure>
<p>It could also be driven by competition with other, similar species. Species may diverge into different size categories to partition their resources and avoid direct competition.</p>
<p>In many cases, there may be no strong or single selective force that is driving the miniaturisation at all, but instead it could simply be a process of random change in the population, which occurs in all organisms over time. This is further driven by population bottlenecks as the smaller and smaller animals get cut off from other populations. </p>
<p>The simple answer is that we just don’t know yet in any of the cases, and it is likely that in most it is a combination of factors. We are much better able to say what the correlates of miniaturisation are – that is, the suite of features, behaviours, and ecologies that accompany miniaturisation – than the causes.</p>
<h2>Does Madagascar have an unusually high number of mini creatures?</h2>
<p>Speaking only of reptiles and amphibians, maybe, but it is hard to say for sure. South-East Asia has <a href="https://www.nationalgeographic.com/animals/article/120111-smallest-frogs-vertebrates-new-species-science-animals">a massive diversity of miniaturised frogs</a>, for instance, but whether the number of major miniaturisation events in that region is greater or less than in Madagascar is difficult to say for sure. </p>
<p>The same goes for Central and South America, where there are plenty of tiny amphibians and reptiles, including salamanders, frogs and lizards. </p>
<p>Ultimately, even though Madagascar may not be the world champion in terms of the number of miniaturised reptiles and amphibians, I think it does stand out as an exceptionally interesting place in which to study their evolution, and we are only just starting to scratch the surface of this.</p>
<h2>What does their tiny size tell us about evolutionary processes?</h2>
<p>This is the question I find the most exciting. From miniaturisation we can learn all kinds of interesting things about physiology, evolution and biomechanics – how organisms move and function.</p>
<p>For instance, there appears to be a pattern where the evolution of miniaturisation is associated with changes in ecology. Almost all miniaturised frogs in Madagascar are terrestrial, irrespective of whether their ancestors were terrestrial arboreal (living in trees). The only conditions under which miniaturised frogs have remained arboreal throughout miniaturisation has been when they reproduce in the water cavities at the base of certain plants’ leaves, such as the <em>Pandanus</em> plant.</p>
<p>We have also learned that the microhylid frogs of Madagascar have mostly miniaturised by retaining juvenile-like characteristics, known as paedomorphosis. For instance, they all have relatively large heads and eyes for their body sizes.</p>
<p>But one species, <em>Rhombophryne proportionalis</em>, has apparently miniaturised by proportional dwarfism. It has the approximate proportions of a non-miniaturised Rhombophryne. So, although paedomorphosis may be the typical way that Malagasy frogs miniaturise, it is by no means the only way that they can miniaturise. </p>
<p>Another particularly interesting finding is that miniaturisation has apparently evolved again and again in different lineages. This was already evident in frogs at the global scale (there are miniaturised frog lineages throughout the tropics). But one group of frogs in Madagascar has done this five or more times alone. This tells us that the evolution of miniaturisation can occur frequently and may be advantageous under certain circumstances. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/391412/original/file-20210324-23-hbq4me.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/391412/original/file-20210324-23-hbq4me.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/391412/original/file-20210324-23-hbq4me.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/391412/original/file-20210324-23-hbq4me.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/391412/original/file-20210324-23-hbq4me.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/391412/original/file-20210324-23-hbq4me.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/391412/original/file-20210324-23-hbq4me.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">Brookesia tuberculata from northern Madagascar was for some time held to be the smallest species of chameleon, but has been repeatedly upstaged. Its real claim to fame, however, is that it has by far the largest hemipenis relative to its body length of any chameleon.</span>
<span class="attribution"><span class="source">Mark D. Scherz</span></span>
</figcaption>
</figure>
<p>From our work on miniaturised chameleons, we have also found that, as these lizards shrink, their genitals increase in relative size. We think that this is because the females are larger than the males. Because the male genitals must couple with those of the females for successful reproduction, and because the female is not as small as the male, the male’s genitals are constrained to remain proportional to the size of the female, even while his body size evolves to be smaller.</p>
<p>There are hundreds of open questions in the field of tiny vertebrate studies. We are just beginning to understand how widespread and common this trait is, how many species have done it, and how many miniaturised species remain undescribed. There is a whole miniature frontier of interesting research to be had among these tiny vertebrates, and I, for one, am excited to see what we discover next.</p><img src="https://counter.theconversation.com/content/157633/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark D. Scherz 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>Madagascar stands out as an exceptionally interesting place in which to study the evolution of “mini” creatures. And we are only just starting to scratch the surface of this.Mark D. Scherz, Research scientist, Technical University BraunschweigLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1357032020-04-21T13:34:08Z2020-04-21T13:34:08ZCurious Kids: can chameleons change colour when they sleep?<figure><img src="https://images.theconversation.com/files/329050/original/file-20200420-152563-vampma.JPG?ixlib=rb-1.1.0&rect=0%2C137%2C1889%2C1155&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A Furcifer pardalis (panther chameleon) sleeps in a tree in Madagascar.</span> <span class="attribution"><span class="source">Mark D. Scherz</span></span></figcaption></figure><p><em>Curious Kids is <a href="https://theconversation.com/africa/topics/curious-kids-36782">a series</a> for children in which we ask experts to answer questions from kids.</em></p>
<p><strong>Can chameleons change colour when they sleep? (Ikechukwu, 6, Lagos, Nigeria)</strong></p>
<p>What a great question, Ikechukwu! It doesn’t have a simple answer, though: yes, chameleons do change colour when they sleep, but we think it happens in a different way to when they’re awake. People like me who study chameleons know quite a lot about chameleons and their colours when they are awake and moving around, but there’s still more to learn about what is going on when they sleep.</p>
<p>Chameleons are really special reptiles, with a whole bunch of special features that make them look very different from all other lizards: they have eyes that can look in two directions at once, a tongue that they shoot out to catch prey, weird grasping hands, and a prehensile tail that they use to hold on while they climb around in trees and bushes.</p>
<p>Around half of all chameleons (there are over <a href="https://www.livescience.com/51061-chameleon.html">200 species</a>) are found on the island of Madagascar, which is where I do <a href="http://www.markscherz.com/">my research</a> and is quite close to the coast of Tanzania in East Africa. The other half are found in mainland Africa, Asia, and in parts of southern Europe. </p>
<p>All chameleons are able to change colour at least a little bit, but some species can do it much more than others. Usually, their colours are quite neutral – plain colours that don’t attract a lot of attention, which is important when they are looking for prey. They don’t want the creatures they eat to see them coming, so they stick to the kinds of colours that are all around them: the browns and greens of sticks and leaves and the sand.</p>
<p>It’s different when the chameleons see predators that want to eat them, or other chameleons of their own species or other species. Then, many chameleon species, especially the big ones, can change to all sorts of colours.</p>
<p>That all happens when they are awake. What about when they sleep? </p>
<h2>Controlling colour</h2>
<p>Chameleons change colour by contracting and relaxing certain cells in their skin that contain either crystals or pigments. The crystals are colourless or slightly yellow, but by lining them up in a certain way, they can be made to reflect certain colours of light, like blue. Pigments, on the other hand, have their own colours, like red or black.</p>
<p>When chameleons are awake (they sleep about as much as we do) they control this process, probably without even thinking about it, like the way the hair on your arms stands on end when you are cold or frightened. That means that when the chameleon sleeps, the colour control is relaxed. Sleeping chameleons become light in colour, probably because certain pigment cells that absorb light relax.</p>
<p>This is actually the best way to find chameleons: if you shine a torch on a sleeping chameleon, its light skin reflects the torchlight, making it easy to see. But while you have the torch on the chameleon, wait a few seconds and you will notice that it gets darker. In fact, if you then move to look at the chameleon close-up, you’ll see that the side you had the torch shining on is darker than the other side. Even better, if you had a leaf covering part of the area that you had the torch shining on, the area of skin behind the leaf would stay light green, while the area exposed to light would darken. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/329077/original/file-20200420-152571-714lpf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/329077/original/file-20200420-152571-714lpf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/329077/original/file-20200420-152571-714lpf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/329077/original/file-20200420-152571-714lpf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/329077/original/file-20200420-152571-714lpf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/329077/original/file-20200420-152571-714lpf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/329077/original/file-20200420-152571-714lpf.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">A sleeping Calumma ambreense, which is a species of chameleon.</span>
<span class="attribution"><span class="source">Mark D. Scherz</span></span>
</figcaption>
</figure>
<p>Chameleons don’t seem to be able to do this – make some parts of their skin lighter than others – when they’re awake. That means the active colour change is different from the one that is used at night. Scientists like myself think that what happens at night might be made possible by light on the skin itself, like the torch you shine on that sleeping chameleon in your garden or at the park.</p>
<h2>More to learn</h2>
<p>Since chameleons are such interesting lizards, you would think that we had already studied them in so much detail that we knew everything there is to know about them. But actually, scientists like me still have lots and lots to learn. One of those things will be to understand more about sleeping chameleons and the ways they change colour. Finding out this new information is one of the things that makes being a scientist so exciting – you never stop learning!</p>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to africa-curiouskids@theconversation.com. Please tell us your name, age, and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/135703/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark D. Scherz 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>All chameleons are able to change colour at least a little bit, but some species can do it much more than others.Mark D. Scherz, Research scientist, Technical University BraunschweigLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1308142020-02-09T07:40:45Z2020-02-09T07:40:45ZKenyan fossil shows chameleons may have ‘rafted’ from mainland Africa to Madagascar<figure><img src="https://images.theconversation.com/files/312847/original/file-20200130-41532-ma59tk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Parsons chameleon, Calumma parsonii, in Andasibe - Analamazaotra National Park, Madagascar</span> <span class="attribution"><span class="source">Artush/Shutterstock</span></span></figcaption></figure><p>Chameleons (Chamaeleonidae) are a family of unique lizards with <a href="https://www.livescience.com/51061-chameleon.html">unusual characteristics</a>: rapidly extendable tongues, feet with two toes pointing forward and two backward, a prehensile tail, and eyes that can move independently of each other. Many species also have the ability to change the colour of their skin. </p>
<p>There are about <a href="http://reptile-database.reptarium.cz/advanced_search?taxon=Chamaeleonidae&submit=Search">213 species</a> of chameleons in the world. They can be found in Africa, the Middle East, southern India, Sri Lanka and the Mediterranean region of Europe. About <a href="https://www.nationalgeographic.com/animals/reptiles/m/mellers-chameleon/">half</a> of all species occur in Madagascar, a large African island in the Indian Ocean. </p>
<p>This island is therefore considered to be a centre of diversity for these lizards and there’s a long-held view that chameleons originated on Madagascar and came to mainland Africa through oceanic dispersal: they <a href="https://www.nature.com/articles/415784a">floated</a> on huge rafts made of trees.</p>
<p>But little is known about how these lizards spread across the world and how they evolved. Their fossil record, the only form of direct evidence about their early evolution and history, is <a href="https://www.sciencedirect.com/science/article/pii/S0016699510000732">very scant</a>. </p>
<p>A <a href="https://royalsocietypublishing.org/doi/full/10.1098/rspb.2013.0184">study</a> in 2013 challenged this view. It suggested that chameleons likely originated in mainland Africa, rather than in Madagascar. It did this by analysing genetic information. But a key element was missing: a fossil chameleon of the right age and in the right place. This would give clear evidence of their history and evolution. </p>
<p>My colleagues and I <a href="https://www.nature.com/articles/s41598-019-57014-5">did research</a> on a chameleon fossil skull from Kenya. The fossil was first <a href="https://www.jstor.org/stable/1565027?origin=crossref&seq=1">discovered</a> in 1992. </p>
<p>We wanted to observe all the elements of the fossil’s skull in detail so that we could place its evolutionary history. The results were a surprise: the chameleon was from a genus that only exists in Madagascar today. Our study of this fossil chameleon skull shows that these chameleons could in fact have originated in Africa. This idea is supported by evidence which shows that <a href="https://www.nature.com/articles/nature08706">ocean currents</a> at the time moved towards Madagascar, allowing animals to make the journey from the continent to the island on rafts made of trees.</p>
<h2>African origins</h2>
<p>The fossil comes from Rusinga Island, a <a href="http://scholar.harvard.edu/files/catryon/files/tryon_etal_2012_azania.pdf">famous fossil site</a> in Kenya. It is one of the oldest chameleon skull fossils, and the only known complete early Miocene (about 18 million years ago) specimen. It is remarkably complete and well-preserved. </p>
<p>However, it’s not been fully freed from the rock and there’s still sediment that fills the whole internal region of the skull. This conceals many bone elements. </p>
<p>We used a micro-CT scanner to give us an x-ray image of all the skull’s internal cavity, including the bones, surfaces and sutures. By looking at these features we could determine which species it most resembled. This modern, non-invasive technology is a very powerful science tool, allowing us to study fossils in a new way.</p>
<p>We found that it was a <em>Calumma</em> species of chameleon – but it was a new one, so we created a new name for it: <em>Calumma benovskyi</em>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/312850/original/file-20200130-41490-rcdx5f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/312850/original/file-20200130-41490-rcdx5f.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=182&fit=crop&dpr=1 600w, https://images.theconversation.com/files/312850/original/file-20200130-41490-rcdx5f.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=182&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/312850/original/file-20200130-41490-rcdx5f.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=182&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/312850/original/file-20200130-41490-rcdx5f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=228&fit=crop&dpr=1 754w, https://images.theconversation.com/files/312850/original/file-20200130-41490-rcdx5f.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=228&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/312850/original/file-20200130-41490-rcdx5f.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=228&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
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</figure>
<p>Since all species of this genus are endemic to Madagascar, and none exist anywhere else in the world today, this fossil uniquely shows that <em>Calumma</em> existed on continental Africa in the past. </p>
<p>Our results challenge the long-held view that chameleons originated from Madagascar and dispersed over water to Africa. It provides strong evidence of an African origin for some Malagasy lineages. </p>
<h2>Rafting chameleons</h2>
<p>At the time when the fossilised chameleon lived, the position of Madagascar relative to Africa was about the same as it is today. The separation of Madagascar from Africa <a href="https://science.sciencemag.org/content/220/4592/67.long">had already</a> occurred, during the age of dinosaurs, approximately 150 million years ago.</p>
<p>The presence of a Malagasy lineage on continental Africa during the early Miocene might appear as a surprise, but other endemic Malagasy animals – such as the <a href="https://www.nature.com/articles/s41467-018-05648-w">Aye-Aye</a> – have had similar patterns. Their fossils have been found on the continent, suggesting an African origin. </p>
<p>The idea is that animals might have used rafts of trees to cross from the continent to the island. Rafting has <a href="https://www.tandfonline.com/doi/abs/10.1017/S1477200003001099">been suggested</a> for many other lizards, so it is not unusual. </p>
<p>Why couldn’t it have got from Madagascar to Africa in the past? The answer lies with looking at how ocean currents flowed in the past. </p>
<p>With regards to chameleons and Africa, oceanic currents favoured eastward dispersal – away from Africa towards Madagascar – at that time of the Eocene until the end of the early Miocene, between 50 to 15 million years ago. So the dispersal would’ve only been possible towards Madagascar. </p>
<p>A <a href="https://www.nature.com/articles/nature08706">study</a> shows that shortly after the early Miocene, the currents between Africa and Madagascar turned in the opposite direction: westwards, toward Africa. This is what’s happening in present-day surface-water circulation. From the middle Miocene onwards, currents would have hindered a journey to Madagascar for any non-swimming animals. </p>
<p>Madagascar’s isolation from the continent supported the further evolution of its terrestrial animals and its exceptional biodiversity. These chameleons then continued to spread and evolve on the island, accounting for the many different endemic species.</p>
<p>To see the chameleon skull, a big piece of the puzzle for this lizard’s history, you can visit the palaeontology section at the <a href="https://www.museums.or.ke/introduction/">Nairobi National Museum</a>, where it is housed.</p><img src="https://counter.theconversation.com/content/130814/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrej Čerňanský receives funding from the Alexander von Humboldt Foundation, the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences
</span></em></p>This fossil find provides strong evidence of an African origin for some Malagasy chameleon lineages.Andrej Čerňanský, Scientist, Comenius University, BratislavaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1227232019-09-17T11:35:28Z2019-09-17T11:35:28ZWhy the global Red List mislabels the risk to many species<figure><img src="https://images.theconversation.com/files/292453/original/file-20190913-8668-1puc05w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The conservation concern about these _Mantidactylus_ frogs has been underestimated - until now.</span> <span class="attribution"><span class="source">Mark D. Scherz</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>When we talk about how threatened animals or plants are, we will almost always reference their statuses on the <a href="https://www.iucnredlist.org/about/regional">Red List</a>. Created by the <a href="https://www.iucn.org/about">International Union for Conservation of Nature</a> – a global organisation that seeks to direct and shape conservation efforts – the Red List uses <a href="https://www.iucnredlist.org/resources/summary-sheet">a set of criteria</a> to evaluate the extinction risk of thousands of species and subspecies. </p>
<p>On the Red List, species are given a rank on a scale of least concern (no conservation action needed), near threatened (almost qualifies for one of the threatened categories), vulnerable (at risk of falling down the scale), endangered (conservation action needed), and critically endangered (urgent conservation action needed). There are also three kinds of extinct; regionally extinct, extinct in the wild, and extinct. </p>
<p>Finally, there are two more categories that don’t say anything about the threat status of the organisms: data deficient (we don’t know enough) and not evaluated (we haven’t figured it out yet, but wanted to keep its name on the list).</p>
<p>The Red List is the only one of its kind. While there are other organisations that have similar goals of assessing the conservation concern of species, the Red List is the only one to do so across all organisms at a global scale. </p>
<p>But, as my colleagues and I argue in a <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0219437">recent paper</a>, the International Union for Conservation of Nature Red List can be inaccurate because it fails to acknowledge uncertainty, specifically taxonomic uncertainty. That is, uncertainty about how organisms are named, defined and classified according to their shared characteristics or how they evolved. </p>
<p>The result is that poor assessments are made on the basis of poor quality data quality. This could lead to the misallocation of resources with widespread costs, including the loss of a species without realising it. </p>
<h2>Species complexes</h2>
<p>One way that taxonomic uncertainty can manifest is in the form of species complexes. Species complexes are when more than one species masquerades under the same name. Sometimes the species are difficult, or impossible, to tell apart.</p>
<p>A huge number of “species” are actually turning out to be species complexes. Giraffes, for example, <a href="https://www.nationalgeographic.com/news/2016/09/wildlife-giraffes-africa-new-species-conservation/">may be four species, not just one</a>. And the African elephant is actually <a href="https://www.livescience.com/9182-african-elephant-separate-species.html">two separate species</a>: the forest and Savannah elephant. They are as evolutionarily different from each other as lions and tigers are from one another. </p>
<p>In smaller, less intensively studied species, complexes are much more frequent.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/292474/original/file-20190913-8653-109puua.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/292474/original/file-20190913-8653-109puua.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=386&fit=crop&dpr=1 600w, https://images.theconversation.com/files/292474/original/file-20190913-8653-109puua.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=386&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/292474/original/file-20190913-8653-109puua.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=386&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/292474/original/file-20190913-8653-109puua.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=485&fit=crop&dpr=1 754w, https://images.theconversation.com/files/292474/original/file-20190913-8653-109puua.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=485&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/292474/original/file-20190913-8653-109puua.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=485&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><em>Mantidactylus (Hylobatrachus) petakorona</em>, a species that we named in our new paper. It is a member of the <em>Mantidactylus (Hylobatrachus) lugubris</em> species complex, which is widespread in the rainforests of eastern Madagascar.</span>
<span class="attribution"><span class="source">Mark D. Scherz</span></span>
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</figure>
<p>Often, we find out about species complexes more or less by accident; we sequence the DNA of a bunch of animals, only to find out that they are not all the same thing, but in fact two or more different things. This is the surest method to realise that you are working with a species complex, but it’s not the only one. For instance, we can find out we are working with a frog species complex when we realise that they have different mating calls.</p>
<p>Ultimately, species complexes can be resolved but it needs careful taxonomic research, often using more complex methods – like DNA analysis. </p>
<h2>What species complexes mean for the Red List</h2>
<p>How organisms are classified – their taxonomy – is the cornerstone of extinction risk assessments. Because of this, major uncertainties in taxonomy, like the case for species complexes, should be grounds for assessment as data deficient on the IUCN Red List. </p>
<p>But the <a href="https://www.iucnredlist.org/resources/redlistguidelines">IUCN guidelines</a> strongly discourage the use of data deficient. They encourage the use of even minimal data to assess the species into one of the other categories. This means that even if only one animal of a certain species has ever been found, it can still be assigned a threat category. </p>
<p><a href="https://www.iucnredlist.org/resources/redlistguidelines">The guidelines</a> also suggest that species complexes should be assessed as a single species, even if they are known to actually be several species. As a result a single species within it can go extinct without anyone noticing.</p>
<p>These policies need to be revised. </p>
<p>In our paper we argued that belonging to or constituting a species complex should qualify a “species” as data deficient for the Red List. </p>
<p>By listing species complexes as data deficient, we can highlight the fact that taxonomy is a vital part of the conservation of species; that it is important, and needs to be funded and promoted as a first step in the protection of many species. </p>
<p>Governments must also recognise the importance of taxonomy-focused fieldwork. All too often permitting agencies are refusing permits looking at species complexes, because they perceive the name to be clarified when it appears on the Red List.</p><img src="https://counter.theconversation.com/content/122723/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark D Scherz is a member of the IUCN SSC Amphibian Specialist Group for Madagascar</span></em></p>The Red List ranks species based on how threatened they are. But it can be inaccurate.Mark D. Scherz, Research scientist, Technical University BraunschweigLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/215432013-12-16T15:22:30Z2013-12-16T15:22:30ZColourful language: chameleons talk tough by changing shade<figure><img src="https://images.theconversation.com/files/37881/original/7svmbzk3-1387203728.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Them's fighting words. And colours.</span> <span class="attribution"><span class="source">Megan Best</span></span></figcaption></figure><p>Humans have been fascinated by the colour-changing abilities of chameleons for a long time. Aristotle himself, the forefather of Western philosophy and also a keen zoologist, mentioned the lizard’s ability in his <em>Historia Animālium</em>, noting that the “change of colour takes place over the whole body,” suggesting the chameleon had a “timorous soul”.</p>
<p>The reasons chameleons change colour vary, including in response to temperature and light, and certainly the background-matching behaviour that comes to mind when most think of a chameleon. But a 2008 study of the South African dwarf chameleons <a href="http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0060025">provided compelling evidence</a> that evolution has favoured the ability to stand out against one’s background rather than blend in – to impress potential mates, for example. This, coupled with behavioural descriptions of rapid colour change during social interactions, strongly suggests chameleons have evolved their dynamic colour palette as a means of communication.</p>
<p>To understand how an animal’s colours can serve as reliable signals to others requires an objective means of quantifying such colours and colour changes. Luckily there have been a number of <a href="http://link.springer.com/article/10.1007%2Fs00265-010-1097-7">recent</a> <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8312.2007.00725.x/abstract">advances</a> in the photographic quantification of colours. Scientists can now use pictures to quantify animal colouration, and use mathematical and physiological models to get an impression of how colours and shades would stimulate an animal’s photoreceptors. In other words we can use photography and computing to measure the colours of animals in the way that animals see them.</p>
<h2>Colour me angry</h2>
<p>In <a href="http://rsbl.royalsocietypublishing.org/content/9/6/20130892">a study</a> published in the journal Biology Letters, we used these photographic techniques to quantify the colour and colour changes of chameleons – as seen by chameleons – during aggressive social interactions. Our research focused on contests between adult male veiled chameleons (<em>Chamaeleo calyptratus</em>), a species known for its pugnacious disposition.</p>
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<p>By filming and photographing the encounters from behind a blind we examined the recordings of each chameleon throughout the trial. The aim was to measure the colour of 28 different body regions in order to uncover if and how the colours were linked to the chameleons’ behaviour. Not knowing whether to focus on the speed of colour change, the amount of colour change, or the final colouration displayed, we measured all three.</p>
<p>We found that the lairy lizards most likely to approach their opponents, thereby escalating an encounter, were those that displayed the brightest stripes. This suggests that a male chameleon stepping into a fight may be able to assess just how keen his opponent is by evaluating the brightness of his opponent’s stripes.</p>
<p>What’s more, we also discovered chameleons with more brightly coloured heads whose colours changed more quickly were more likely to <em>win</em> aggressive encounters. So if you, as a chameleon, quarrel with another who reveals an intensely coloured, rapidly changing head – something that should be apparent as he marches directly towards you – then you may have messed with the wrong lizard.</p>
<p>But what benefit comes from signalling to your competitor information about your motivation or fighting ability? It seems that by flagging up very brightly its willingness to rumble in the jungle, the chameleon can ensure aggressive encounters are less costly. Considering a fight could potentially result in serious injury, it’s much better if opponents can be made to back down, without any physical contact being made.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/37882/original/3k58xs7c-1387204102.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/37882/original/3k58xs7c-1387204102.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=821&fit=crop&dpr=1 600w, https://images.theconversation.com/files/37882/original/3k58xs7c-1387204102.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=821&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/37882/original/3k58xs7c-1387204102.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=821&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/37882/original/3k58xs7c-1387204102.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1032&fit=crop&dpr=1 754w, https://images.theconversation.com/files/37882/original/3k58xs7c-1387204102.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1032&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/37882/original/3k58xs7c-1387204102.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1032&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">I <em>am</em> smiling.</span>
<span class="attribution"><span class="source">Megan Best</span></span>
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</figure>
<p>This seems to be what is happening with chameleons, where we found that many contests between aggressive chameleons were resolved without any physical fisticuffs. If the information content of chameleon colour signals was perfect, no contests would actually need to escalate into the head-butting, lunging, biting fracas that we regularly observed. This suggests that chameleons can get information from one another based on their colour, but that this information isn’t always 100% reliable – or that they choose to ignore it in a display of rash, headstrong behaviour. Just like humans do, in other words.</p>
<h2>True colours … or not</h2>
<p>Humans have devised many and varied means to exchange information with one another, from words to morse code to email. However, as we can frequently influence the behaviour of others from what we communicate, there is sometimes a temptation to misrepresent ourselves, or the truth. Lying can sometimes provide short-term benefits to the liar, but there are frequently large costs in being identified as an unreliable person. These costs exist in the animal kingdom as well, albeit in different forms, and are thought to play a role in the evolution of stable signalling strategies.</p>
<p>While our recent work suggests chameleons possess the means to communicate information through their colour changes, we don’t yet understand how these colourful messages are interpreted, how they influence behaviour, and what mechanisms ensure that a chameleon can accurately assess competitors based on external appearance. Time to get back to the chameleons! </p><img src="https://counter.theconversation.com/content/21543/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Russell A. Ligon 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 have been fascinated by the colour-changing abilities of chameleons for a long time. Aristotle himself, the forefather of Western philosophy and also a keen zoologist, mentioned the lizard’s ability…Russell A. Ligon, PhD Candidate, Arizona State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/138422013-05-02T20:11:02Z2013-05-02T20:11:02ZHow do chameleons and other creatures change colour?<figure><img src="https://images.theconversation.com/files/23061/original/83npgp4r-1367365986.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rapid colour change may occur due to various "triggers" – but what are they?</span> <span class="attribution"><span class="source">Today is a good day</span></span></figcaption></figure><p>When most people think of colour change, they think of octopuses or chameleons - but the ability to rapidly change colour is surprisingly widespread.</p>
<p>Many species of crustaceans, insects, cephalopods (squid, cuttlefish, octopuses and their relatives), frogs, lizards and fish can change colour.</p>
<p>They all have one thing in common: they are ectotherms (animals that cannot generate their own body heat in the same way as mammals and birds) and only ectotherms have the specialised cells that enable colour change.</p>
<p>Watch the first 20 seconds of the video below – it will blow your mind:</p>
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<p>Colouration in animals is produced by reflection and scattering of light by cells and tissues, and by absorption of light by chemical pigments within cells of the skin.</p>
<p>In ectotherms, cells containing pigments are called <a href="https://en.wikipedia.org/wiki/Chromatophore">chromatophores</a> and are largely responsible for generating skin and eye colour.</p>
<h2>Vertebrate colour changers</h2>
<p>In vertebrate ectotherms (such as frogs, lizards and fish), there are three main types of chromatophore:</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/23133/original/ntxgfrfv-1367457110.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23133/original/ntxgfrfv-1367457110.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/23133/original/ntxgfrfv-1367457110.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=819&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23133/original/ntxgfrfv-1367457110.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=819&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23133/original/ntxgfrfv-1367457110.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=819&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23133/original/ntxgfrfv-1367457110.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1029&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23133/original/ntxgfrfv-1367457110.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1029&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23133/original/ntxgfrfv-1367457110.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1029&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cape dwarf chameleon (Bradypodion pumilum).</span>
<span class="attribution"><span class="source">Adnan Moussalli and Devi Stuart-Fox</span></span>
</figcaption>
</figure>
<ul>
<li>xanthophores, which contain yellow-red pigments</li>
<li>iridophores containing colourless stacks of crystals or platelets that reflect and scatter light to generate hues such as blues, white and ultra-violet</li>
<li>melanophores, which contain black melanin pigment</li>
</ul>
<p>The melanophores play a crucial role in colour change.</p>
<p>They are large, star-like cells with long “arms” (dendrites) that extend towards the skin’s surface. </p>
<p>Colour change occurs due to the movement of “packets” of melanin pigment (melanosomes) within the melanophores.</p>
<p>When melanin pigment is aggregated within the centre of the cell, the skin appears very pale, whereas when it is dispersed through the arms of the melanophores towards the skin’s surface, the animal appears dark.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/23062/original/vgx3d5cm-1367367311.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23062/original/vgx3d5cm-1367367311.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/23062/original/vgx3d5cm-1367367311.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23062/original/vgx3d5cm-1367367311.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23062/original/vgx3d5cm-1367367311.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23062/original/vgx3d5cm-1367367311.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23062/original/vgx3d5cm-1367367311.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23062/original/vgx3d5cm-1367367311.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"></span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>Because the arms of the melanophores extend between and over the other types of chromatophore (generating yellows, reds, blues, etc.), varying the degree of dispersion of the melanin can conceal or reveal those chromatophores, thereby varying the animal’s colour.</p>
<p>Colour change may also occur due to changes in the spacing of the stacks of platelets or crystals within the iridophores, which changes the way they reflect and scatter light, and therefore their colour.</p>
<h2>Cephalopods’ tricks</h2>
<p>In cephalopods, the structures known as chromatophores are very different to those of vertebrates.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/23063/original/hqkq24ty-1367367653.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23063/original/hqkq24ty-1367367653.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/23063/original/hqkq24ty-1367367653.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23063/original/hqkq24ty-1367367653.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23063/original/hqkq24ty-1367367653.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23063/original/hqkq24ty-1367367653.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23063/original/hqkq24ty-1367367653.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23063/original/hqkq24ty-1367367653.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cuttlefish can completely change colour in less than a second.</span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
</figcaption>
</figure>
<p><a href="http://tolweb.org/accessory/Cephalopod_Chromatophore?acc_id=2038">Cephalopod chromatophores</a> contain a pigment-filled sac, surrounded by radial muscle fibres.</p>
<p>These muscles contract to change the size and shape of the pigment-filled sac (e.g. thin, flat disc vs small sphere), resulting in the near-instantaneous and dramatic colour change.</p>
<p>Underlying the chromatophores in cephalopods are two other types of cells:</p>
<ul>
<li>iridophores, which are much the same as iridophores in vertebrates</li>
<li><a href="http://tolweb.org/notes/?note_id=2646">leucophores</a>, which appear white</li>
</ul>
<p>When the pigment sacs are contracted, these other cells are revealed, changing the colours we see.</p>
<p>So although colour change in cephalopods and chameleons both involve chromatophores, the chromatophores are very different structures, as is the mechanism of colour change.</p>
<p>In chameleons, colour change occurs due to the movement of pigments within chromatophores, whereas in cephalopods, colour change occurs due to muscle-controlled “chromatophore organs” changing the shape of pigment sacs.</p>
<h2>Pull the trigger</h2>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/w9ecX8PRPSw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Rapid colour change may occur due to various “triggers” including temperature or light (a reflexive response via light-sensitive receptors in skin).</p>
<p>That’s why chameleons are very pale at night when asleep but darken as soon as a torch is shone on them (and only on the side with the light shining on it).</p>
<p>Most importantly, animals change colour in response to their surroundings (including variations in background colour, presence of predators, mates or rivals).</p>
<p>They need to assess their surroundings so that they know what colour to change to.</p>
<p>Information about an animal’s surroundings (from the senses) is processed by the brain and the brain sends signals directly, or via hormones, to chromatophores.</p>
<h2>All change</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/23132/original/8g5csjzy-1367457045.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23132/original/8g5csjzy-1367457045.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/23132/original/8g5csjzy-1367457045.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=433&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23132/original/8g5csjzy-1367457045.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=433&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23132/original/8g5csjzy-1367457045.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=433&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23132/original/8g5csjzy-1367457045.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=544&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23132/original/8g5csjzy-1367457045.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=544&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23132/original/8g5csjzy-1367457045.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=544&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 dominant male knysna dwarf chameleon (Bradypodion damaranum) on the left and a submissive one on the right – you can see the big difference in colours.</span>
<span class="attribution"><span class="source">Adnan Moussalli and Devi Stuart-Fox</span></span>
</figcaption>
</figure>
<p>Colour change is a very useful ability.</p>
<p>Given that colour-changing animals cannot generate their own body heat, colour change can help animals to regulate their body temperature.</p>
<p>So, when cold, a lizard may be dark because dark colours absorb more heat, whereas when hot, a lizard may become very pale because light colours reflect heat.</p>
<p>But perhaps the two most important functions of colour change are camouflage and communication.</p>
<p>Colour change allows animals to flash bright colours to warn rivals or attract mates, while remaining camouflaged at other times.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/02zvS_QdJhw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Male giant cuttlefish use moving waves of black and white stripes in aggressive and courtship displays (see video above), while chameleons show <a href="http://www.environmentalgraffiti.com/featured/mood-chameleon-colour/14886">an impressive range</a> of conspicuous colour patterns.</p>
<p>Yet, when they are not communicating to each other, they are superbly camouflaged.</p>
<p>Colour change allows unparalleled flexibility, which is perhaps why we find it so fascinating.</p><img src="https://counter.theconversation.com/content/13842/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Devi Stuart-Fox receives funding from the Australian Research Council</span></em></p>When most people think of colour change, they think of octopuses or chameleons - but the ability to rapidly change colour is surprisingly widespread. Many species of crustaceans, insects, cephalopods (squid…Devi Stuart-Fox, Senior Lecturer and ARC Australian Research Fellow, Zoology, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.