It’s five o'clock on a summer morning in Winnipeg. Our research team is unloading a series of small traps from the trunk of our car, which is parked on a residential road. Using a stick, we slather peanut butter from a huge jar into each trap as bait and quietly sneak into the yards we’ve been given permission to enter, placing the traps in suitable locations.
A dogwalker gives us a suspicious glance as they walk by. Traps now set and open, we wait. This effort is to investigate how animals respond to urbanization and what traits enable them to colonize and persist in cities.
Urban ecology and evolution are still relatively new fields of study — for a long time, researchers preferred to study nature in remote locations farther away from human influence. But a growing number of scientists are now studying the ecology and evolution of animals and plants found in our own backyards, reflecting a realization that cities are important ecosystems where plants, animals, humans and other organisms coexist.
Yet these cities are challenging places for wildlife and plants. Cities are hot, noisy and polluted. The numerous buildings, cars, pets and, of course, people going about their business pose many dangers to the species that increasingly share our living quarters.
The remaining natural vegetation is also altered in cities. For example, interest in gardening has introduced many new plants and trees to cities that aren’t found in nearby natural areas. These complex and intertwining environmental modifications can make finding food, a suitable mate or a safe shelter challenging for most animals, and make it difficult for native species of plants to thrive in cities.
What does it take to thrive?
So, what enables some species to succeed in city living, where other species fail? One of the most important qualities in urban animals is their ability to change their behaviour, coming up with innovative ways to socialize, avoid dangers or cope with challenging urban environmental conditions.
For example, mountain chickadees that nest in cities are bolder than their rural counterparts in Kamloops, B.C. Urban coyotes avoid humans (and particularly their cars) by being more active at night in Edmonton. And rosy-faced lovebirds use air-conditioning vents to cool off on hot days in Phoenix, Ariz.
Read more: How coyotes and humans can learn to coexist in cities
We also see evidence of rapid evolution in cities, where the genetic material of a population is changing. Urban water fleas, for example, grow and mature faster and can withstand higher temperatures than rural water fleas. Anolis lizards in Puerto Rico have evolved longer limbs and more toe lamellae — fine scales on the bottom of their feet — in cities, traits that may help individuals better cling to smooth urban surfaces like glass, metal or painted concrete.
Recently, researchers wanted to know just how widespread these kinds of rapid evolutionary changes are across our cities. A global team of researchers — led by University of Toronto scientists and including team members from both my former University of Manitoba lab, and my department at Concordia University — teamed up to answer this question using the humble clover plant.
The Global Urban Evolution project (or GLUE) underscores the important role of cities as testbeds to advance our understanding of the natural world, and evolutionary ecology in particular.
Clover is ubiquitous in cities across the world so researchers visited parks, lawns and roadsides to collect samples from 160 cities and surrounding areas on five continents (gathering a few more suspicious glances from dogwalkers along the way). Considered among “the best replicated test of parallel evolution, on the largest scale ever attempted,” results suggest clover populations are indeed adapting to urban environments worldwide.
As the GLUE project shows, research undertaken in cities can help us better understand basic ecological and evolutionary processes and mechanisms. This knowledge can also help us protect declining species, which is critical as we face the dual challenges of biodiversity loss and climate change.
If urban species are evolving, and seemingly before our very eyes, that means biodiversity conservation and management goals are moving targets. Understanding how species are changing over time can help us to better plan and manage for greener, more biodiverse cities. This, in turn, has important implications for the well-being of the 55 per cent of the world’s human population who call an urban area home.
Studying an urbanizing world
Back in Winnipeg, a trap in a nearby yard is rattling. A tiny red squirrel has found the peanut butter breakfast and is now full — and also stuck. It’s time for me to get to work. I weigh and measure the squirrel, and then mark it for future identification. Ultimately, this work will tell us how squirrels alter their activity in cities, for example by waking up earlier compared to squirrels in more natural areas, as has been found for urban birds.
So, the next time you notice someone catching squirrels in your neighbourhood, collecting clover on lawns or water fleas in city ponds, you might just be witnessing an urban evolutionary ecologist hard at work, trying to discover just what makes their favourite species successful at city living.