Update – December 2019

We’re thrilled to see interest in the SquirrelMapper project continuing to increase. Since our last update we’ve surpassed 2000 registered volunteers on Zooniverse. At iNaturalist over 18,000 people have contributed squirrel photos and nearly 5000 people have helped to confirm the species identification in those photos. We also recently launched a “Find the Squirrel” game that appears to be a hit. The game will help us understand whether the camouflage of gray and black squirrels differs in a variety of habitats. Finally, Dr. Kristin Winchell recently published a very nice article about the SquirrelMapper project at the Life in the City blog. Check out their blog for all kinds stories about the evolution of life in cities.

Here at Zooniverse we’ve now classified the coat color of squirrels from 36,501 images from around the world. We extracted a subset of nearly 25,000 images to look for spatial patterns of color morph frequencies. Many of the photos are excluded from analysis because they don’t have a squirrel or the coat color of the squirrel is ambiguous. For now we’re also just focusing on images with a single squirrel, which make up the vast majority of images. The bulk of the observations continue to come from eastern North America where gray squirrels are native, but we’re seeing squirrel observations in new places where they are introduced in Europe (e.g., France):


The map below shows the color morphs are squirrels in the United States and Canada (red dots = black morph, gray dots = gray morph). Places where the shade of the dots are darkest represent places with the most observations of each squirrel morph.


Here’s a different kind of map with the squirrel color morphs. Each circle represents a single squirrel and indicates the color morph (black or gray). This map also shows different land cover types (e.g., green = forest, red = urban, brown = agriculture). Observations of black squirrels are layered on top of observations of gray squirrels. This view shows that black squirrels are common in the far north where it is cold, but they also tend to cluster around cities.


Here’s a view of Europe, where the vast majority of squirrel observations continue to be of the gray morph:


Thanks again to everyone who has contributed to the SquirrelMapper project! We’ll be back with more data in January.

Mapping squirrel color morphs - September 2019


The SquirrelMapper project on Zooniverse started in July 2019. We’re delighted to see that more than 1000 people have contributed to classifying the coat color of eastern gray squirrels in just two months. Over at iNaturalist we’ve had over 15,000 contributors of squirrel photos and nearly 4000 participants help identify the squirrels observed in those photos. Thanks to all the citizen scientists for making this project a success.

This is a brief update on patterns we’ve observed with the data collected up to September 12, 2019. At that point 13,199 squirrel photos have been classified for coat color by at least 10 people. The bulk of the observations have been from the eastern U.S. and southeastern Canada where gray squirrels are native, but we’ve also received observations from places where gray squirrels have been introduced, including the U.K., Ireland, Italy, South Africa, and a handful of cities in western North America. Here’s a map of the worldwide distribution of squirrels classified here on Zooniverse:

Not all of the 13,199 make it to the data analysis stage. Some photos don’t actually include a physical squirrel (e.g., tracks in snow), and sometimes there’s not agreement among observers on how many squirrels are present or the coat color of those squirrels. The patterns shown below are based on 10,629 photos of a single physical squirrel where there was at least 80% agreement among observers on on the squirrel’s coat color.

The map below shows the color morphs are squirrels in the United States and Canada (red dots = black morph, gray dots = gray morph). Places where the shade of the dots are darkest represent places with the most observations of each squirrel morph. Black squirrels are most common in the northern part of the eastern gray squirrel’s native range, and they tend to cluster around cities, particularly Toronto, Detroit, and Cleveland, as well as cities along the U.S. east coast. We know black squirrels have a thermal advantage over grays in the winter, but they can be quite prevalent even in places with moderate temperatures, such as the introduced populations near Vancouver, Can and the San Francisco Bay Area in California.

Here’s another map showing the distribution of color morphs in North America, this time with the data summarized as the percentage of black squirrels in a standard grid. This map shows largely the same pattern but should be interpreted with caution because some grid cells have very few squirrel observations.

Here’s the situation in Europe, where the vast majority of squirrel observations have been of the gray morph:

That’s it for now. Many thanks to all the citizen scientists who are contributing to this project!