About Tamiasciurus hudsonicus fremonti (Audubon & Bachman, 1853)
Description: Red squirrels (American red squirrels) can be easily distinguished from other North American tree squirrels by their smaller size, with a total length (including tail) of 28–35 cm (11–14 in), their territorial behavior, and their reddish fur paired with a white venter, or underbelly. They are somewhat larger than chipmunks. The Douglas squirrel is morphologically similar to American red squirrels, but Douglas squirrels have a rust-colored venter and are restricted to the southwestern coast of British Columbia and the Pacific Northwest of the United States. The ranges of American red squirrels and Douglas squirrels overlap in southern British Columbia, northwestern Washington and eastern Oregon. Distribution: American red squirrels are widely distributed across the North American continent. Their range includes most of Canada (excluding northern areas with no tree cover, the southern half of Alberta, and the southwestern coast of British Columbia), the southern half of Alaska, the Rocky Mountains area of the United States, and the northern half of the eastern United States. American red squirrels are abundant and not of conservation concern throughout most of their range. They were introduced to Newfoundland and have lived there in abundance for decades. The endangered subspecies grahamensis, found only on Mt. Graham, Arizona, was formerly considered a member of this species, but is now classified as a subspecies of the southwestern red squirrel Tamiasciurus fremonti. Reproduction: American red squirrels are spontaneous ovulators. Females enter estrus for only one day, but leave their territory before ovulation; these exploratory trips may function to advertise their upcoming estrus. On the day of estrus, multiple males chase the female in an extended mating chase. Males compete with one another for the chance to mate with the estrous female. Estrous females will mate with 4 to 16 males. Reported gestation length ranges from 31 to 35 days. Females can breed for the first time at one year of age, but some delay breeding until two years of age or older. Most females produce one litter per year, but some skip reproduction in some years, while a subset of females breed twice in other years. Litter sizes typically range from one to five, and most litters contain three or four offspring. Offspring are pink and hairless at birth and weigh approximately 10 g. While nursing, offspring grow at an average rate of 1.8 g per day, and reach adult body size at 125 days. They first emerge from their natal nests at around 42 days, but continue to nurse until approximately 70 days. Nests are most commonly built from grass in the branches of trees. Nests may also be excavated from witches' broom (abnormally dense vegetative growth caused by a rust disease), or in cavities in the trunks of spruce, poplar, and walnut trees. American red squirrels rarely nest below ground. Each individual squirrel maintains several nests within its territory, and females with young move their offspring between nests. There are reports of red squirrels nesting within human dwellings, using insulation as nest material. A three-year study of a red squirrel population in southwest Yukon found that female red squirrels had high levels of multiple-male mating, and would even mate with males that shared similar genetic relatedness. Parental relatedness had no effect on the neonatal mass, growth rate, or first-year survival rate of offspring.
