Red squirrels (Sciurus vulgaris) are rodents found across a wide range of habitats, including coniferous forests and broadleaf woodlands throughout Eurasia. Understanding their reproductive cycle is important for comprehending their biology and how they adapt to different environments.
The Mating Season
Red squirrels typically mate during two distinct periods each year. The primary mating season generally occurs from late winter to early spring, specifically February to March. A secondary breeding period often takes place in mid-summer, usually June to July. Mating can sometimes begin as early as December or January on warmer days.
During these periods, females are receptive for only a single day within each cycle. Multiple males often compete to mate, leading to energetic “mating chases” through trees and across the ground. These chases can be noisy, involving chirping and calling. The heaviest or most dominant male often secures the right to mate with the female.
Environmental Influences on Breeding
The timing, duration, and success of red squirrel breeding are affected by environmental factors. Food availability is a primary determinant, with abundant conifer seeds and other mast crops playing a large role. Females require a minimum body weight, typically 280-300 grams, to breed. When food resources are plentiful, females are more likely to reach this condition, which can lead to earlier breeding and potentially two litters a year.
Conversely, food scarcity can delay or suppress breeding, as females may not accumulate enough fat reserves to support reproduction. Weather conditions also influence breeding patterns. Severe cold or prolonged snow cover can delay the onset of the breeding season, while unusually warm temperatures in late winter might accelerate it. Stored food from the previous autumn helps mitigate the impact of harsh winter conditions on a female’s ability to reproduce.
From Mating to Offspring
Following successful mating, red squirrel females undergo a gestation period typically ranging from 35 to 42 days. The young, known as kits or pups, are born within a drey. Dreys are usually spherical nests made of interwoven twigs, often located in tree hollows or high in tree branches, and lined with soft materials like moss, leaves, and grass for insulation.
A typical litter consists of three to seven kits, though this number can vary, with some litters containing as few as one or as many as eight. At birth, kits are blind, deaf, and hairless, weighing approximately 10 to 18 grams, and are entirely dependent on their mother for care. The mother squirrel provides all nursing and protection, as males do not participate in raising the young.
Their eyes open around 28 to 30 days of age, and they begin to develop fur. Kits usually start venturing outside the drey around seven weeks old and are typically weaned by eight to ten weeks of age, gradually transitioning to solid foods.