The family Sciuridae encompasses tree squirrels, ground squirrels, and flying squirrels, all of which follow specific reproductive cycles. Squirrels do have a mating season, and for many commonly observed species, this reproductive period occurs more than once annually.
The Bimodal Reproductive Cycle
Many familiar tree squirrels, such as the Eastern Gray Squirrel, adhere to a bimodal reproductive cycle, meaning they have two distinct mating seasons each year. The first breeding period typically occurs in late winter, often peaking in January or February. This timing ensures the first litter is born in early spring, coinciding with increasing food availability.
The second reproductive window opens in mid-to-late spring and continues into the summer, generally peaking around June or July. The exact timing of both cycles is influenced by local conditions, primarily climate severity and the abundance of food resources. Older, more experienced females usually produce two litters per year, while younger females may only breed once.
How Mating Seasons Differ Across Species
While the bimodal cycle is common for many tree squirrels, reproductive timing varies significantly across the squirrel family. Ground squirrels, including marmots and prairie dogs, generally adhere to a monomodal cycle, mating only once per year. Their breeding season is tightly synchronized with their emergence from hibernation in early spring, typically lasting only a few weeks.
Flying squirrels also display variation based on species and location. The Northern Flying Squirrel tends to reproduce only once annually, with mating occurring in late spring between late March and May. In contrast, the Southern Flying Squirrel often follows a bimodal pattern, with breeding periods in early spring and again in the summer months.
Mating Behaviors and Reproductive Outcomes
The onset of the mating season is signaled by the female entering a short period of receptivity, or estrus, which may last less than a day. During this time, she releases pheromones that attract males from a considerable distance. This chemical signal triggers the mating chase, where multiple males vigorously pursue the single receptive female.
The chase is a form of competition, with the most dominant male typically earning the right to mate. Males may communicate with loud chattering or “buzzing” vocalizations, and aggressive interactions between rivals are common. After successful copulation, the female drives the male away, as males do not participate in raising the young.
Gestation and Kits
Following mating, the female enters a gestation period that lasts between 38 and 46 days. She gives birth to a litter, which usually contains two to five young, though litters can range from one to eight. The newborn squirrels, called kits, are born blind, deaf, and hairless, relying entirely on the mother for warmth and nourishment.