This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: By comparing variations in the coat colors of eastern gray squirrels (Sciurus carolinensis) in Montreal city parks, researchers found that hyperlocal conditions appear to play a bigger role in shaping wildlife traits than previously thought. Despite its name, the eastern gray squirrel can sometimes have a black coat.
The researchers found that squirrel coat colors across the Montreal region are shaped not only by urbanization but also by factors such as forest canopy cover and the presence of the St. Lawrence River and its tributaries, which can limit movement and create distinct populations. The findings are published in the Journal of Animal Ecology.
"I visited almost 200 parks around the city on my bicycle during my free time the first summer that I was at McGill, and observed over 800 squirrels, some of which were gray and others were black," said Francis Quang-Hai Dinh, the study's first author, who was an undergraduate student at McGill when he collected information about the squirrels. The researchers also gathered data through park surveys and citizen science observations. Gray-coated squirrels tend to be seen most frequently in Montreal.
Although gray coats predominated throughout the city, the researchers found that the proportion of black (melanic) squirrels was highest in areas with cooler winter temperatures and greater forest canopy cover. The heat-retention advantages of darker coats may have offered a biological advantage in cooler winter weather. Contrary to patterns found in many cities, black squirrels were generally less prevalent in Montreal's more urbanized areas.
This result will require further examination, the researchers said. The findings highlight how wildlife can respond to environmental conditions at a very local scale. Cities are not uniform habitats but complex landscapes where differences between neighborhoods, as well as geographic features such as rivers, can influence how animals adapt and evolve over time, the researchers said.
"People often think of cities as a single type of environment, but our findings show that the conditions animals experience can vary dramatically from one neighborhood to another," said Allison Roth, the study's senior author, who was a GRIL postdoctoral fellow in McGill's Department of Biology during data collection. Roth is now an assistant professor at the University of Missouri. "These local differences, along with barriers such as rivers, can shape how wildlife populations evolve, which means we need to look beyond simple urban-rural comparisons to understand adaptation in cities." The study was included in a special feature published by five ecology journals focusing on how researchers are using large, open-access datasets and collaborative approaches to tackle big ecological questions.
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