Researching the Evolution of Life in Cities – Hobart and William Smith Colleges \
The HWS Update

Researching the Evolution of Life in Cities

Recently published research by Associate Professor of Biology Bradley Cosentino explores how cities affect the evolution of coat color in eastern gray squirrels. The research was conducted making use of a trending technique in the natural sciences—using observations from citizen scientists to augment the research team’s work.

Focusing on this common resident of parks and backyards across eastern North America, Cosentino and his co-authors are investigating why melanism in gray squirrels – which produces a black coat color – tends to be common in cities but rare in rural forests. Historically the black morph was common throughout upstate New York and north into Canada, but melanism declined in forests and is hanging on in cities.

“We know very little about how evolution works in cities,” says Cosentino. “Urban ecology has grown tremendously as a discipline, but we know much less about how the dramatic ecological change in cities affects evolution. What makes this project so exciting is the potential for providing the public with a relatable case of evolution-in-action right in their backyards.”

Cosentino’s paper, co-written with James P. Gibbs and Matthew F. Buff  from the State University of New York College (SUNY) of Environmental Science and Forestry, is titled “The Biological System—Urban Wildlife, Adaptation, and Evolution: Urbanization as a Driver of Contemporary Evolution in Gray Squirrels (Sciurus carolinensis).” The research was published as a chapter in the book Understanding Urban Ecology by Springer Nature.

To help find the answers, they created the SquirrelMapper project. The project’s website allows interested individuals to upload images and observations of squirrels, classify the squirrels’ color as well as play a simple game, “Find the Squirrel.” The game allowed the team to gather data on the level of difficulty game players have in spotting black and gray squirrels in rural and urban settings. The data suggest that people can more easily detect the black morph in rural forests, where squirrels are commonly killed by predators and hunters. One of the most common causes of squirrel mortality in cities is vehicular collisions, and the research team found the black morph is less likely to killed by cars than the gray morph. Senior Alessandra Bryan ’20 is currently working on an Honors project to test whether black squirrels are more visible than the gray on asphalt roads, leading to the theory that drivers are better able to avoid hitting the rodents with darker fur.

As Cosentino points out, squirrels make excellent research subjects: they are one of the most well-known animals in the U.S. and are active year-round. Studying their melanism is easily accomplished without the need for trapping or disturbing them. In addition, public interest in the squirrels makes gathering data far more successful than it might be with another species.

“We have a unique opportunity to deepen our understanding of how cities shape the evolution of life for an organism with tremendous public appeal,” says Cosentino.

The public is encouraged to contribute observations of squirrels and to play the “Find the Squirrel” game at the SquirrelMapper project website.