Do squirrels have periods? No. Unlike humans and some other primates, squirrels do not experience menstrual bleeding. Their reproductive cycles operate differently, a common characteristic shared by most mammals.
Understanding Mammalian Reproductive Cycles
Mammals exhibit two primary types of reproductive cycles: estrous and menstrual. These cycles prepare a female’s body for potential pregnancy. The main distinction between these two cycles lies in how the uterine lining is managed when pregnancy does not occur.
In species with an estrous cycle, such as squirrels, the uterine lining is reabsorbed by the body if fertilization does not happen. This means there is no external bleeding. The estrous cycle culminates in a period of heightened sexual receptivity known as estrus, or “heat.”
Conversely, in species with a menstrual cycle, like humans, the uterine lining is shed and expelled from the body through the vagina if pregnancy does not occur. This process results in visible bleeding, commonly referred to as menstruation or a “period.” This difference is why squirrels and many other mammals do not have periods.
The Squirrel’s Reproductive Journey
Squirrels, like many rodents, follow an estrous cycle, with reproductive activity confined to specific breeding seasons. During these times, female squirrels enter estrus, a phase when they are receptive to mating. This estrus period is relatively short, often lasting only a day or less.
Observable signs indicate a female squirrel is in estrus and ready to mate. These include increased vocalizations, such as chirping or chattering, and a noticeable change in behavior, often involving a vigorous chase by multiple males. Male squirrels will pursue the female until one successfully mates with her.
Many squirrel species, including common grey squirrels, typically have two breeding seasons each year. The first occurs in late winter or early spring (December to February), with litters born in late winter or early spring. The second takes place in late spring or early summer (May to June), resulting in litters born in mid-to-late summer.
After mating, the gestation period for squirrels ranges from 38 to 46 days, depending on the species. Grey squirrels, for example, have a gestation period of about 44 days. A female squirrel usually gives birth to a litter of two to four young, though litter sizes can vary from one to eight. The young are born blind and hairless, relying entirely on their mother for care and nourishment during their initial weeks.