Red squirrels become sexually active at about 9 – 10 months of age. The breeding season lasts from around January to September, depending on weather and food availability. There are two peaks of litter production each season, with spring litters produced between February and April, and summer litters between May and September. Not all females breed twice a season and yearling females breed only once in their first year.
Breeding activity in red squirrels is strongly linked to female body condition. Better fed females, in areas with good food supply, give birth to heavier young which in turn are more likely to be weaned successfully.
Females come on ‘heat’ for only a single day. Males living nearby in the forest are attracted to her, probably by smell, and start following her. As more males join in, scuffles occur which sometimes culminate in the female taking flight. This begins a ‘mating chase’ which is characterised by squirrels crashing noisily around in the trees.
Squirrels do not pair-bond and the successful male will not stay with the female after mating. Males try to mate with more than one female and, occasionally, females will mate with more than one male.
Gestation lasts 36 – 42 days and squirrels can give birth to up to six young in a litter (although the average is three young). They weigh approximately 10 – 15 gm and are born naked, blind and deaf. Hair develops after 8 – 9 days and their eyes and ears open at around 3 to 4 weeks. The young are covered in dense fur by the end of the third week and the tail becomes brush shaped at the end of the fourth week. They begin to explore the nest’s surroundings and feed on solids at 7 – 8 weeks of age. They are generally weaned after 8 – 10 weeks and leave the drey weighing about half their adult weight.
