Francis Quang-Hai Dinh dedicated his initial summer at McGill University to a unique endeavor – scouring Montreal’s parks on his bicycle in pursuit of squirrels. Covering close to 200 green spaces spanning from Mirabel to Saint-Bruno, Dinh meticulously observed and documented over 800 grey and black squirrels. What started as a simple undergraduate task soon evolved into a personal passion project aimed at unraveling the influence of the city’s layout and meandering watercourses on the process of evolution.
Expressing his growing fascination with squirrels, Dinh remarked, “I fell in love with them after I had started staring at them for long enough and just giving them enough thought. We don’t even think of squirrels as being animals. They’re practically just pests, but they are indeed wildlife.” Lacking access to a car and facing limited public transportation options in suburban regions, Dinh heavily relied on his bicycle to traverse extensive distances, making him the sole documented researcher to manually survey squirrels park by park throughout the area.
The study unveiled a significant concentration of black squirrels in northern areas. While approximately 12% of squirrels in Montreal exhibit black coloration on average, the prevalence of black squirrels escalates as one moves further north. Regions just beyond Laval boasted up to 40% black squirrels, with the island of Laval showcasing about 20% black squirrels, the island of Montreal around 15%, and the south shore of Montreal merely 2-3%, according to Dinh, currently pursuing integrative biology studies at the University of Illinois Urbana-Champaign.
The research identified three primary factors contributing to this phenomenon, with temperature emerging as the foremost influencer. The cooler climates in northern regions favor black squirrels due to their superior heat-absorbing black coloration. Additionally, the density of forest cover plays a crucial role, as a thicker tree canopy provides a darker backdrop where black squirrels can blend in more effectively.
Allison Roth, the senior author of the study and an assistant professor at the University of Missouri, emphasized that the research transcends mere squirrel observations. Rather, it serves as a model to explore how urban environments propel evolutionary adaptations. Roth highlighted the intricate environmental variations within cities, such as Montreal’s diverse neighborhoods, varying tree coverage, and distinctive waterways, like the St. Lawrence River, which create microhabitats fostering genetic and physical changes in animal populations.
The study, titled “Fine-scale spatial variation in eastern grey squirrel melanism across a complex urban landscape,” delves into the nuanced alterations occurring within wildlife populations on a neighborhood-specific basis, challenging the conventional belief that human development is the primary driver of such transformations. Urban sprawl, altering local temperatures and reducing tree cover, combined with natural barriers like river systems, collectively shape the evolutionary landscape for urban wildlife.
Published as part of a special feature by five ecology journals focusing on collaborative data-driven research to address significant ecological inquiries, the study sheds light on the intricate interplay between urbanization, environmental factors, and wildlife adaptations. Dinh, reflecting on his experience, expressed a newfound perspective on wildlife, recognizing the resilience of nature amidst urban modifications.