Squirrels are common throughout the world and occur naturally in North and South America, Europe, Asia and Africa. Their abundance is perhaps supported by the fact that there are well over 250 squirrel species, including types of ground squirrels, tree squirrels, chipmunks, marmots and flying squirrels. Still, most of these small to medium-sized rodents share similar breeding habits.
Finding a Mate
After about 10-12 months of age, the majority of female squirrels become fertile at the beginning of each new year. Around this time, they emit scents and vocalizations that attract male squirrels from a variety of neighboring territories. Males abandon their routines to seek out fertile females. Males competing for female attentions will fight with one another to claim dominance, which is not only a factor of size and strength, but of maturity. (Older males tend to win these battles.) Once dominance has been established, female squirrels become aware of which males are the most eligible bachelors. The female gives chase, sometimes at the same time that her suitors are battling. Those males that can keep up only further prove their suitability as partners.
Generally, female squirrels mate with more than one partner multiple times over the course of anywhere from two days to several weeks. The actual mating process takes about a minute and often ends when the male squirrel's penis "plugs" the female's vagina with a non-seminal, wax-like substance. This plug works as a barrier against the sperm of other males who might mate with the female after the original partner has had his turn. This is likely one of the reasons that the majority of squirrel litters are sired by a single male, despite any given female having multiple partners.
Larger tree and flying squirrels (like fox and gray squirrels) usually have gestation periods of anywhere between 38 and 46 days, while smaller species often gestate for less than 38 days. Tropical and African species of squirrel have been known to gestate up to 65 days. In turn, ground squirrels usually gestate between 29 and 31 days.
Female squirrels birth between one and five babies at a time, though some reports have noted up to nine young squirrels in a single litter. Birthing takes place in the female's nest, which has usually been nestled into a tree or burrow, depending on the species. Newborn squirrels are hairless, helpless with eyes closed and ear flaps folded toward the skull. They will nurse for up to nine weeks.