The Douglas squirrel is native to the North American regions facing the Pacific. Although Douglas squirrels quickly become accustomed to human presence, humans can pose a threat to them, as they collect pine cones for seeds used in forestry and cut down primary forests.
However, squirrel numbers do not appear to have declined with commercial forest exploitation. Infact, IUCN does not include the Douglas squirrel among the endangered species. They are territorial animals. In winter, each squirrel occupies a territory of around 10,000 m², but during the mating season the breeding pairs defend a single territory together.
The groups of squirrels that are often seen during the summer are probably young specimens belonging to the same brood.
Douglas squirrel and the clearing of primary forests
Douglas squirrels live in coniferous forests from the Sierra Nevada Mountains of California in the south to the coastal regions of British Columbia and southeast Alaska in the north.
They prefer primary or mature secondary forests, and some scholars believe that they play an important role in their ecosystem.
They are active during the day, throughout the year, and often squeak loudly at intruders.
During summer nights, they sleep in spherical nests that they themselves build in trees, but in winter they use tree cavities as shelter. Douglas squirrels feed primarily on seeds of conifers such as Douglas fir, Sitka spruce, and lodgepole pine, but they also eat acorns, berries, mushrooms, bird eggs such as the yellow warbler, and some fruits, including strawberries and plums.
Unlike many other tree squirrel species, they lack cheek pouches in which to carry food. They store food supplies, and during the autumn they bury pine cones. They often remove the scales of the pine cones to reach the seeds in the same place, called a mound.
Discarded flakes can accumulate over years, forming piles more than a meter wide, as the same site is used by generations of squirrels. Their predators include American martens, bobcats, house cats, common goshawks and owls.