The Species of Eastern Gray Squirrel

March 1st was an ordinary day for almost everyone at PRISMS. During physical activity period, someone was chasing after a Frisbee behind Albemarle when everyone else suddenly stopped him. Right in front of his feet, there sat a small squirrel. It looked around innocently, not knowing why a bunch of people were watching him and took a few steps forward. A whisper moved the crowd, “Let’s go. I think we’re scaring it.” A few seconds later, there were only two people remaining while they pointed with cameras at the squirrel. He was even more confused.

Another person walked across the field and started talking with the two. The squirrel looked at the new person, being the tallest among the trio, curiously trying to figure out if he was a moving tree by climbing onto his shoe. The atmosphere went kind of awkward until the tall guy asked the others, “Can you guys tell which species does it belong to?”

The correct answer is: What we found was an eastern gray squirrel (Sciurus carolinensis).

This term may sound very familiar to you. Although you may not notice them or pay much attention to these creatures, the eastern gray squirrel is the kind of squirrel that we usually see on campus. Hopefully, by the end of this article, you will have a better understanding of them.

The word “squirrel”, derived from the Greek word σκίουρος (ski-o-dos) meaning shadow-tailed, can point to not just the small rodent that we just saw. It can point to any of the animals in the family Sciuridae, generally typified by soft fur, large eyes, a fluffy tail, and a primarily herbivorous diet while most of the species in the family also feed on insects.

Different animals classified as "squirrels". Picture source: Chicoutimi, Karakal AndiW, Markus Krötzsch, Nico Conradie, and Hillewaert Sylvoille

What we usually call squirrels

You may have noticed that some squirrels have entirely black fur. These squirrels are a variant of the eastern gray squirrel species that has a condition named “melanism” which means the development of dark pigment in the skin. This condition can occur in multiple species including large cats, chickens, and guinea pigs.

Black Eastern Gray Squirrel

Simple answer, because their major habitat in nature was mostly the middle and eastern states of the United States. Aside from that, they have been introduced to other regions in the world such as Italy, South Africa and the United Kingdom where they are considered invasive species because their existence is threatening the native species in these areas.

Distribution map of Eastern Gray Squirrels, Picture source: Enceclopedia of Life

For example, in the British Isles, the native squirrel species are Eurasian red squirrels (Sciurus vulgaris), who have less ability to process certain toxins in acorns than eastern gray squirrels. As a result, they are outcompeted in their homeland by their evolutionary “cousins” who belong to the same genus with them.

The diet of eastern gray squirrels mainly consists of nuts, acorns, tree bud, insects and sometimes bird eggs. Squirrels have powerful incisors that allow them to penetrate nutshells, this gives them the ability to eat nuts as their staples.

Squirrel skull. Picture source: Skulls Unlimited

Besides nut shells, these powerful incisors can also bite through your hands. So if you see a squirrel running around on campus, don’t try to feed it with your hand. They are satisfied with the bird feeder behind the dorms.

An eastern gray squirrel and the bird feeder, Photo credit: Melinda Lu

The powerful incisors of the eastern gray squirrel also gave them the ability to strip tree bark off a tree to consume the inner bast and cambian layers. This act causes damage to a lot of trees.

Although eastern gray squirrels almost never worry about food, that doesn’t mean they live without any risks because a lot of predators in the wild such as hawks, foxes, and raccoons see squirrels as food. For the squirrels living in the city, domestic dogs and cats are their major threats.

A cat eating a squirrel, picture source: wikimedia

As a species of tree squirrel, eastern gray squirrels do not hibernate like ground squirrels. The way they survive through the long cold winters of New England is that they store acorns and seeds around the “dens” that they make for dwelling and remember those locations using their spatial memory and usage of landmarks. Before winter comes, they estimate energy consumption and store fat inside their bodies according to their estimation. Because of that, they tend not to come out when the weather is bad or when it’s cold outside. Who would want to come out of their warm and cozy rooms when it’s snowing outside? And that’s why everyone needs snow days.

But they'll come out during spring again :) Photo credit: Melinda Lu

Acknowledgments

Author: Melinda Lu

Editor: Edward Shi, Johan Kramer, Paddy Liu, and Stephanie Zhao (sorted by first name)

Cover photo: Melinda Lu

Thanks to Mr. Carpenter and Tracy Han for providing suggestions.

Special thanks to Joshua Huang.

References

“Diseases Squirrels Can Transmit to Humans.” Diseases Squirrels Can Transmit to Humans, www.crittercontrol.com/services/squirrels/diseases-squirrels-can-transmit-to-humans.html.

“VetzInsight.” Veterinary Information Network (VIN) - For Veterinarians, By Veterinarians, www.vin.com/vetzinsight/default.aspx?pid=756&%3Bid=5454945.

Sciurus caroliensis, Global Invasive Species Database, http://www.iucngisd.org/gisd/speciesname/Sciurus+carolinensis

“Sciurus Carolinensis.” Sciurus Carolinensis (Eastern Gray Squirrel, Gray Squirrel, Grey Squirrel), IUCN, www.iucnredlist.org/details/42462/0.

Sciurus carolinensis (grey squirrel), Invasive Species Compendium, https://www.cabi.org/isc/datasheet/49075

Gurnell, John, et al. "Alien species and interspecific competition: effects of introduced eastern grey squirrels on red squirrel population dynamics." Journal of Animal Ecology 73.1 (2004): 26-35.

Melanism, Merriam-Webster, https://www.merriam-webster.com/dictionary/melanism

Squirrel, Oxford English Dictionary, https://en.oxforddictionaries.com/definition/squirrel

“Eastern Gray Squirrel.” Penn State University, www.psu.edu/dept/nkbiology/naturetrail/speciespages/graysquirrel.htm.

Jacobs, L. F., & Limant, E. R. (1991). Gray squirrels remember the locations of buried nuts. Princeton University.

Davies, Caroline. “The Ultimate Ethical Meal: A Grey Squirrel.” The Observer, Guardian News and Media, 10 May 2008, www.theguardian.com/lifeandstyle/2008/may/11/recipes.foodanddrink.

Cat + Squirrel Picture source: wikimedia commons https://commons.wikimedia.org/wiki/File%3A%D0%A1at_caught_a_squirrel%3B_Ust'Labinsk.jpg