Quick answers
| Question | Answer | Scope | Source | Checked |
|---|---|---|---|---|
| Do tree squirrels hibernate? | No. Tree squirrels stay active and live on stored nuts through the winter. | Tree squirrels; Oregon State page on the western gray squirrel | Oregon State University Extension | |
| Do ground squirrels hibernate? | Yes. Wyoming ground squirrels go underground in late July or early August and stay there until March or April. | Wyoming ground squirrel, Florissant Fossil Beds (Colorado) | NPS, Florissant Fossil Beds National Monument | |
| What they eat | Acorns, nuts, seeds, fruit, corn, insects and mushrooms, and now and then garbage. | Eastern fox squirrel, Missouri National Recreational River | NPS, Missouri National Recreational River | |
| Summer foods | Green plants, berries and insects on top of their usual nuts. | Western gray squirrel, Oregon | Oregon State University Extension | |
| How long they live | 1 to 6 years on average. | Eastern gray squirrel, Lowell (Massachusetts) | NPS, Lowell National Historical Park | |
| Pregnancy and litter size | A pregnancy of at least 6 weeks and a litter of one to five, most often two or three. | Western gray squirrel, Oregon | Oregon State University Extension | |
| How much they weigh | 18 to 33 ounces as adults. | Western gray squirrel, Oregon | Oregon State University Extension | |
| What eats squirrels | Bobcats, weasels, coyotes, hawks, owls and snakes, among others. | Western gray squirrel, Oregon | Oregon State University Extension |
In the sources’ own words
Do tree squirrels hibernate?
Oregon State University Extension, Wildlife in the Garden: Western Gray Squirrel (EC 1572)“Tree squirrels don't hibernate. They store nuts to last through the winter.”
Scope: Tree squirrels; Oregon State page on the western gray squirrel
Do ground squirrels hibernate?
National Park Service, Florissant Fossil Beds National Monument, Squirrels“The squirrels enter their burrows in late July or early August and hibernate until the following March or April.”
Scope: Wyoming ground squirrel, Florissant Fossil Beds (Colorado)
What they eat
National Park Service, Missouri National Recreational River, Squirrels“…they eat a wide variety of foods like acorns, nuts, seeds, fruits, corn, insects, mushrooms, and occasionally garbage.”
Scope: Eastern fox squirrel, Missouri National Recreational River
Summer foods
Oregon State University Extension, Wildlife in the Garden: Western Gray Squirrel (EC 1572)“In the summer, squirrels also eat green vegetation, berries, and insects.”
Scope: Western gray squirrel, Oregon
How long they live
National Park Service, Lowell National Historical Park, Squirrel“Average Lifespan: 1 - 6 years…”
Scope: Eastern gray squirrel, Lowell (Massachusetts)
Pregnancy and litter size
Oregon State University Extension, Wildlife in the Garden: Western Gray Squirrel (EC 1572)“Female squirrels give birth after being pregnant for at least 6 weeks. A litter can range from one to five young, though two or three seem common.”
Scope: Western gray squirrel, Oregon
How much they weigh
Oregon State University Extension, Wildlife in the Garden: Western Gray Squirrel (EC 1572)“Adults weigh between 18 to 33 ounces.”
Scope: Western gray squirrel, Oregon
What eats squirrels
Oregon State University Extension, Wildlife in the Garden: Western Gray Squirrel (EC 1572)“Squirrels are eaten by bobcats, weasels, coyotes, hawks, owls, snakes, and other predators.”
Scope: Western gray squirrel, Oregon
What these sources do not say
- Whether all ground squirrels keep the same dates. The July-to-April timing is for Wyoming ground squirrels at one park.
- A lifespan for western gray or fox squirrels. The only figure here is for the eastern gray squirrel.