Red Squirrel - Reproduction and Mortality

Reproduction and Mortality

Mating can occur in late winter during February and March and in summer between June and July. Up to two litters a year per female are possible. Each litter usually contains three or four young although as many as six may be born. Gestation is about 38 to 39 days. The young are looked after by the mother alone and are born helpless, blind and deaf and weigh between 10 and 15 g. Their body is covered by hair at 21 days, their eyes and ears open after three to four weeks, and they develop all their teeth by 42 days. Juvenile red squirrels can eat solids around 40 days following birth and from that point can leave the nest on their own to find food; however, they still suckle from their mother until weaning occurs at 8 to 10 weeks.

During mating, males detect females that are in œstrus by an odor that they produce, and although there is no courtship, the male will chase the female for up to an hour prior to mating. Usually multiple males will chase a single female until the dominant male, usually the largest in the group, mates with the female. Males and females will mate multiple times with many partners. Females must reach a minimum body mass before they enter œstrus, and heavy females on average produce more young. If food is scarce breeding may be delayed. Typically a female will produce her first litter in her second year.

Red squirrels that survive their first winter have a life expectancy of 3 years. Individuals may reach 7 years of age, and 10 in captivity. Survival is positively related to availability of autumn–winter tree seeds; on average, 75–85% of juveniles die during their first winter, and mortality is approximately 50% for winters following the first.