Beasts of the Urban Wild

One of Aesop’s fables tells the tale of two cousins, a city mouse and a country mouse who visit each other in their respective homes. The country mouse lives simply and peacefully, on a diet of roots and foraged acorns. The city mouse enjoys banquet feasts of sweets and meats left out on the dining table, but has to contend with the dangers of living in close quarters with humans — as well as their animal companions like cats and dogs. At the end of the story, the mice return to where they belong, each of them sure that they are living the best life.

This fable, which is at least 2,000 years old, foreshadowed a divide in the animal kingdom that has continued into the present. Urban areas don’t just provide a different kind of habitat for animals, they can change the animals that live there into creatures particularly suited to their new environments. As a result of these changes, a city mouse must stay a city mouse.

Synurbanization — the changes wildlife make to adapt to urban environments — affects many species of plants and animals. Studies show that plants responding to the presence of herbivores and the water availability in cities pass on urban-specific genes to their seedlings. Some urban fish have developed more streamlined bodies compared to their rural counterparts, the better to move in urban streams that usually flow faster and which can be prone to unpredictable flash floods during heavy rains as a result of concrete and other impenetrable surfaces in cities.

Populations of certain bird species that usually migrate across oceans now overwinter in urban areas thanks to the availability of food and the warmer microclimates of human-built environments. Other species of birds have longer breeding seasons in cities for similar reasons. Urban birds, writes Maciej Luniak of Warsaw’s Institute of Zoology, start singing earlier in the morning and end later at night — a circadian rhythm disruption that may or may not be caused by artificial lighting or some other aspect of urban life.

These types of changes happen in mammals as well. Toronto’s raccoons offer a notorious example. In 2002, the city of Toronto started a city-wide composting program. Raccoons were particularly big fans of it because it required residents to put all their edible food into green bins that the animals quickly learned how to get into on trash nights. Human designers improved the bins, and the city spent $31-million dollars on bins they hoped were “raccoon proof”; the masked creatures learned how to break into these new bins as well. Suzanne MacDonald, a psychologist who studies raccoon and other animal behavior at York University in Toronto, has posited in interviews that the city’s efforts might have served as an accidental training program of sorts for particularly adept raccoons who solve one puzzle and happily move on to the next one humans put in front of them.

Tove Danovich is our new columnist. Her column, “Beyond Human,” will explore our relationship with the more-than-human world and how our evolving ideas of wildness shape the ways in which we see and value the environments around us. Photo by Jamie Bosworth.

MacDonald set out to test how urban raccoons fared against rural raccoons in the task of opening a garbage can fitted with a bungee cord, and found a notable difference. While 17 out of 22 urban raccoons observed in the study opened the can and enjoyed the dinner placed inside, none of the 22 rural raccoons observed managed to figure out the puzzle. MacDonald suggested in a paper that this might be an example of “anthropogenic selection” and that living closer to humans and the puzzles of urban life might be making the raccoons who live there smarter, more persistent, and more inclined to explore new things.

The problem is that as more of the world becomes urbanized, not all species will be as adept at altering their behavior as raccoons or metropolitan plants, and some might be left behind, unable to evolve or learn to thrive in concrete jungles. Our urban designs — made by humans for humans — often neglect to consider the ways in which the built environment is a habitat.

But purposeful changes can help cities become a welcoming place for plants and animals. After the Congress Avenue Bridge in Austin, Texas, became the site of the largest urban bat colony in the world, bridge and transportation designers began looking into how new bridges could be built or retrofitted to house bats, many species of which are threatened thanks to disease and habitat loss. Other cities are building wildlife crossings that help animals pass over or under busy roads or otherwise connect fragmented urban greenspaces. While it’s true that a city is not an old-growth forest, there are things we can do to make all types of habitat wilder.

We might also consider changing our perceptions of what it means to be wild. Few humans think of a city as habitat, though it’s an environment like any other. We tend to equate habitat with wilderness — the only way to be wild is to be far away from humans. When I used to live in New York City, I often noted cockroaches, pigeons, and rats. I didn’t consider them part of the local fauna but pests needing to be eradicated. I often yearned to be in the wild, where the animals were, without realizing that they’d been nearby the whole time. The problem wasn’t that urban areas weren’t wild, but only that I wasn’t paying attention.

In the last weeks before I moved, I learned there was a pair of red-tailed hawks that had been living, breeding, and hunting in a nearby park in Manhattan during the entire eight years I’d lived there. In fact, cities can be especially accommodating to some species. New York City may have the largest urban population of peregrine falcons in the world. The cliff-dwelling birds, with mesmerizing black and white striped patterns on the undersides of their wings and tails, have rebounded there after being decimated by pesticide poisoning in the mid-1900s. The city’s tall buildings and window ledges make a tidy substitute to the cliffs they evolved alongside. To them, the metropolis doesn’t look unnatural or unwild. It looks like home.