Pine squirrels love, love, love their pines!


Raise your paw if you love pine trees! Pine squirrels sure do. They’re associated with all things pine — they live in pine forests, nest in pines and depend on pine seeds for food. Meet the only “pine squirrels” in North America: The Douglas’s, American Red and Mearns’s.

DOUGLAS’S SQUIRREL (Tamiasciurus douglasii)

A Douglas's squirrel, one of the so-called pine squirrels, standing on a thin tree branch and outlined by a brilliant blue sky.

Douglas’s Squirrel. (Steve Voght / Flickr; cc by 2.0)

Naturalist John Muir called the Douglas’s (or Douglas) Squirrel the “squirrel of squirrels” because they possess “every attribute peculiarly squirrelish enthusiastically concentrated.” Douglas’s Squirrels are small, only about a foot long, including their tail. They won’t be overlooked, though, as they’re very active and noisy. They have distinct summer and winter coats. In summer, they’re reddish-brown to grayish-brown on the topside. In winter, they’re more grayish overall and may have noticeable ear tufts.

Very high and broad midden that was created by pine squirrels called Douglas's squirrels.

Squirrel midden. (hthrd / Flickr; cc by 2.0)

Douglas’s Squirrels feed on available foods, such as acorns, fruit, mushrooms, buds, and sap, and will visit bird feeders for nuts. Conifer seeds, however, are their main diet. They have a distinctive way of eating pinecones — from the bottom up, rather than top down. In the fall, they bury pine cones to eat later on. They also sometimes store mushrooms in the fork of trees. 

The squirrels often use the same spot year after year where they peel scales off pine cones to get at the seeds. These refuse piles are called middens. Generations of squirrels may use one, with it growing several feet high and wide.

In summer, Douglas’s Squirrels build nests of twigs, mosses, shredded bark and lichens on tree limbs or in tree forks. In winter, they nest in tree cavities or in underground burrows.

The squirrels are solitary, except during mating season, which is late-February to April. Babies are born about one month later. They’ll stay with their mother up to a year, so if you see a group of them it’s probably a mother and her offspring. The average lifespan for Douglas’s Squirrels in about two years. 

Douglas’s Squirrels, sometimes called Chickarees, inhabit West Coast pine forests from California north into Canada and Alaska. They’re named after David Douglas (1799-1834), a Scottish botanist who spent some years traveling in North America.

AMERICAN RED SQUIRREL (Tamiasciurus hudsonicus)

Female American Red Squirrel, called a pine squirrel, and her two babies standing side-by-side on the top of a red fence.

Mother with two of her young. (Gilles Gonthier / Flickr; cc by 2.0)

American Red Squirrels are recognizable by their deep reddish color and their tiny size — only about 6 to 7 inches long, plus a 6-inch tail. They’re the most widely distributed of the pine squirrels, ranging from Alaska and Canada to the Great Lakes region, and south and east along the Rocky Mountains. They inhabit conifer forests, but occasionally mixed forests, too.The females are receptive to mating for one day only, usually about February, and sometimes for one day in about August. On those single days, they often mate with several males. Four to five babies are born 35 to 40 days later. Juveniles have a high mortality in their first year. If they survive it, they may live up to 10 years.

The females are receptive to mating for one day only, usually about February, and sometimes for one day in about August. On those single days, they often mate with several males. Four to five babies are born 35 to 40 days later. Juveniles have a high mortality in their first year. If they survive it, they may live up to 10 years.

An isolated group of red squirrels in southeast Arizona is different enough to be considered a sub-species. Named the Mt. Graham Pine Squirrel (T. hudsonicus grahamenis), they became stranded there when the area around them became desert during the last glacial times (22,000 to 12,500 years ago). There are 24 more recognized red squirrel subspecies, with the main difference between them being where they live. The American Red Squirrel shouldn’t be confused with the Eurasian Red Squirrel, which is in a different genus (Sciurus vulgaris).

MEARNS’S SQUIRREL (Tamiasciurus mearnsi)

A Mearns's Squirrel, one of the so-called pine squirrels, clinging head down to the trunk of a pine tree.

Mearns’s Squirrel. (© Nicolas Ramos-Lara)

Mearns’s Squirrels live in isolation in the open, dry pine and fir forests of the Sierra de San Pedro Mártir mountain range in Baja California, Mexico, and the southern border of California. The heaviest of the pine squirrels, genetic evidence suggests they evolved from Douglas’s Squirrels and became separated from them about 12,000 years ago.

They’ve made unique adaptations to their rugged habitat. For instance, other squirrels are willing to use leaf nests and burrows for nesting, but the Mearns’s will use only tree cavities and only in large diameter trees. This means that suitable live trees and snags are vital to their survival. Another difference is their jaw strength: While the Douglas and Red squirrels can carry pine cones in their mouth, the Mearns’s can carry big ones. Also, unlike the other pine squirrels, they don’t build and defend middens.

Five tiny Mearns's Squirrel babies, so-called pine squirrels, with eyes still closed, huddled together on hard-packed ground.

Mearns’s Squirrel babies. (© Melissa Merrick)

The baby Mearns’s shown above are lying at the base of a tree. There’s a story that goes with them: They were under attack by vicious ants when researcher Melissa Merrick heard their intense cries. Ordinarily, they wouldn’t be out in the open like this, but their mother was moving them from an old nest to a new one. Melissa removed all the ants, which had already caused wounds, and left the pups on a large piece of bark on the ground. She waited nearby and watched as their mother returned and safely carried them all up the tree to a new nest. A happy ending!

Mearns’s are named for Edgar Alexander Mearns (1856-1916), a naturalist and surgeon in the U.S. Army who served for some years in Mexico. They’re now federally listed as threatened in Mexico due to their low population and isolation. The IUCN¹ lists them as endangered. You can learn more about the Mearns’s from Nicolas Ramos-Lara’s study, The Ecology of the Endemic Mearns’s Squirrel.

¹International Union for Conservation of Nature
*Top photo: CC License: cc by 2.0

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