Squirrels are a common sight, often seen scampering through trees or foraging in yards. These agile rodents, known for their bushy tails and acrobatic movements, adapt to various environments. Understanding their reproductive cycles provides insight into how these familiar creatures thrive.
Squirrel Gestation Period
The length of a squirrel’s pregnancy, known as the gestation period, varies depending on the species. For Eastern gray squirrels, gestation lasts between 40 and 45 days, with an average of 44 days. Other tree squirrels, like fox squirrels, have a similar range of 42 to 45 days.
Ground squirrels have shorter gestation periods. For instance, Richardson’s ground squirrels are pregnant for about 23 days, thirteen-lined ground squirrels for 28 days, and California ground squirrels for around 30 days.
Breeding Seasons and Litter Frequency
Most squirrel species, including the Eastern gray squirrel, breed twice annually. The first breeding season occurs from late December or January through February, with litters born in early spring, between February and April. The second breeding period takes place from May to August, with litters born in late summer or early fall, from August to September.
While many females produce two litters per year, younger or less experienced mothers might have only one. Red squirrels can also produce two litters in a year if conditions are favorable. Ground squirrels, however, have only one litter each year. Environmental factors like food availability, weather, and climate influence breeding timing and frequency. A mild winter, for instance, can sometimes lead to an earlier start to the breeding season.
Nesting and Litter Size
Female squirrels prepare a drey, or nest, often constructed from leaves and twigs or located in tree cavities, as a safe place for giving birth. Litters range from one to nine young, averaging two to six. Eastern gray squirrels commonly have two to four young per litter, though they can have up to eight.
Life After Birth: From Kit to Independence
Squirrels are born as helpless young, often called kits or pups. At birth, they are hairless, blind, deaf, and cannot regulate their own body temperature. These tiny kits weigh only about 0.5 to 1 ounce. Their development progresses during their time in the nest.
Kits’ eyes open around four to five weeks, and their ears open around three weeks. Fur appears by three to four weeks, developing into a full coat by seven weeks. Young squirrels start venturing outside the drey to explore at six to eight weeks old. Weaning from their mother’s milk begins around seven weeks and is complete by 10 to 12 weeks. By 10 to 12 weeks old, these young squirrels are independent; some from late summer litters may remain with their mother through the winter.