The Washington ground squirrel can be solitary or live in colonies (1), with females occasionally forming coalitions. These coalitions usually consist of between two and four females, who build burrows and raise their young together, as well as sharing responsibility for defending the burrow from any predators (7). The burrows of the Washington ground squirrel can be up to 1.7 metres deep and over 7 metres long (5).
The breeding season begins shortly after the Washington ground squirrel emerges from hibernation in late January or early February, and lasts for several weeks (1) (5) (8). Emergence from the burrow and breeding can happen up to a month later at higher elevations (1) (5). Males of this species usually emerge from hibernation earlier than the females (5).
The female Washington ground squirrel gives birth to a single litter of between 5 and 11 young in February or early March, after a gestation period of 23 to 30 days (1) (2) (5). The young are weaned and begin to emerge from the burrows in late March, and are nearly adult size by the end of May (1) (5).
In May or June adult Washington ground squirrels enter a period of dormancy, while juveniles generally wait until June or July (1) (2) (8). The hibernation period of the Washington ground squirrel lasts for seven or eight months, leaving only a small proportion of the year for reproducing, foraging and accumulating body fat (1) (8). While it is not hibernating, this species is diurnal and is mostly active in the morning, especially when temperatures are high (1) (2) (5).
The diet of the Washington ground squirrel consists mostly of herbaceous vegetation, as well as flowers, roots, bulbs and seeds as well as insects (1) (2) (5). A high-energy diet is important for providing this species with the necessary body fat reserves to survive its long period of dormancy (7).