Wildlife Wednesday - Ground Squirrels & Tree Squirrels
By Andy Ames
Have you ever wondered what the difference is between a ground squirrel and a tree squirrel? While some differences may be obvious, others may surprise you. The most obvious difference is that tree squirrels are arboreal while ground squirrels are semi-fossorial. This means that tree squirrels primarily live and nest in trees and when alarmed will retreat up a tree. Ground squirrels, on the other hand, spend most of their time on the ground, dig and live in burrows, which they use for nesting, food storage, and safety. Ground squirrels also hibernate during the winter while tree squirrels often harvest and store food for the cold winter months. Physically, tree squirrels have longer tails (good for balance) and longer legs, while ground squirrels have shorter tails and legs (easier to maneuver under ground). Finally, ground squirrels have cheek pouches while tree squirrels do not. Cheek pouches are like reusable grocery bags. Since ground squirrels feed primarily on seeds and berries, this allows them to gather a bunch before heading back to their burrow. Tree squirrels harvest mostly larger items, like pine cones and mushrooms, so can only carry one item at a time. Tree squirrels of the Estes Valley include the Pine squirrel and Abert’s squirrel as well as the occasional Fox squirrel. Ground squirrels include the Wyoming and Golden-mantled.
The most common tree squirrel of the Estes Valley goes by many names — Pine squirrel, Douglas, Red squirrel, or Chickaree. You are often alerted to its presence by its characteristic chattering alarm call. They are prolific harvesters of pine cones, often caching them or burying them for winter use. When retrieved, the Pine squirrel will strip the scales off the cone in order to access the seeds. While Pine squirrels may nest in trees, they often will use a cavity of a log and line it with grass for insulation.
The distinctive Abert’s squirrel is found primarily in Ponderosa pine forests. They rely heavily on the Ponderosa for food — seeds, bark, shoots, and sap, as well as shelter, making their nests high up in the trees.
Golden-mantled ground squirrels may be seen low in trees and bushes but primarily stick to the ground and rocks. They are often confused with chipmunks due to the stripes running down their back and sides. The stripes on chipmunks, however, start from the nose and run all the way down to the base of the tail. Golden-mantled ground squirrels, meanwhile, have a white eye ring and stripes starting at the shoulder.
The longest hibernator of the Estes Valley, Wyoming ground squirrel adults may start hibernating as early as August with juveniles a little later.
The Rock Squirrel is a ground squirrel in a tree squirrel’s body. Physically, it looks a lot like a tree squirrel- long legs with a long bushy tail, but also has a dappled coat, similar to the Wyoming ground squirrel, and cheek pouches like other ground squirrels. It lives in burrows in the ground, often suns itself on rocks, hibernates, and when alarmed may let out a chirp like a marmot. The Estes Valley is in the far reaches of its range in latitude as well as altitude. This one was near Boulder. I have yet to see one in the Estes Valley. Have you?