Squirrels are a common sight across North America. Understanding the timing of their reproductive cycle is helpful for various reasons, such as preventing nesting in homes, observing young, or assisting a distressed animal. Knowing when young squirrels are in their nests and when they venture out can prevent accidental intervention or guide appropriate action.
The Bimodal Birthing Season
Most common tree squirrel species, such as the Eastern Gray and Fox Squirrel, follow a bimodal, or two-season, breeding pattern. This means two distinct litters are typically born each year, correlating with resource availability. The first birth peak occurs in early spring, usually spanning late February into April, following a mating period during the winter season.
The second birthing period follows a similar cycle, with mating occurring in late spring or early summer, around May or June. This results in a second wave of births that peak in late summer or early fall, generally between August and September. The gestation period for tree squirrels averages around 44 days, making the time between mating and the appearance of young in the nest (drey) brief.
Young squirrels, or kits, are born blind and helpless, remaining entirely dependent on their mother for several weeks. They stay confined to the nest for about 10 to 12 weeks before they are fully weaned and begin to venture out. This means young squirrels from the first spring births start appearing outside the nest by late May or June, while the second litter emerges in late fall, often around November.
Species and Climate Influences on Timing
While the bimodal pattern applies to species like the Eastern Gray and Fox Squirrel, the precise timing is influenced by geography and species-specific biology. In warmer, southern regions, the breeding season can begin earlier and extend longer due to milder weather and a continuous food supply. First litters in these areas are often born as early as January or February, shifting the entire season forward.
Conversely, in northern latitudes where winters are harsh, the breeding season is often compressed, and the first litter may not appear until late March or April. The availability of food resources plays a direct role, as a well-fed female is more likely to enter estrus and successfully raise a litter. Some species, like the American Red Squirrel, may have a slightly different schedule, often focusing their birthing periods closer to the summer months.
The timing of births is closely tied to the mother’s health and the local environment’s ability to support her young. A nutritionally stressed female may delay her breeding cycle or fail to produce a second litter. This variability means that while there are two primary seasons, a baby squirrel may be encountered almost any time between late winter and late fall, depending on local conditions.
Developmental Stages of Baby Squirrels
Understanding a young squirrel’s physical development helps determine its age and level of dependence, which is often more useful than relying solely on the calendar date. Newborn squirrels (neonates) are completely hairless, pink-skinned, and have sealed eyes and ears. This makes them entirely reliant on their mother for warmth and feeding during the first two to three weeks of life.
Around four to five weeks of age, the kits’ eyes begin to open, and their fur grows in, giving them a fuzzy appearance. They are more mobile within the nest but are still nursing and cannot survive independently. By six to seven weeks old, they resemble miniature adults, developing the characteristic bushy tail and beginning to explore outside the nest to sample solid foods.
True independence is reached between ten and twelve weeks of age, when the young squirrels are fully weaned and leave the nest for good. A squirrel found outside that is fully furred but smaller than an adult, with a thin tail, is a juvenile still learning to forage. The immediate needs of a young squirrel are best assessed by these physical markers rather than the calendar date.
What to Do If You Find a Young Squirrel
If a young squirrel is found on the ground, first determine if it is truly orphaned or temporarily separated from its mother. The mother will often retrieve her young if they have fallen, but she will not approach if people, pets, or threats are nearby. If the baby is uninjured, place it in a small container, such as a box or basket with a soft cloth, and position it near the base of the tree where it was found.
Keep the baby warm, as a mother will not retrieve a cold kit. Provide warmth by placing a chemical hand warmer, a sock filled with warm rice, or a hot water bottle beneath the cloth. Ensure there is a barrier to prevent direct contact and burns. Observe the area from a safe distance for several hours, as the mother may return to move the baby to an alternate nest.
Never attempt to feed the baby squirrel water or any type of milk replacement, as this can be dangerous and potentially fatal due to aspiration or digestive issues. If the mother has not returned by dusk, or if the young squirrel is visibly injured, bleeding, or cold, immediate intervention is necessary. Contact a licensed local wildlife rehabilitator for guidance, as they possess the training and resources to provide appropriate care and eventual release back into the wild.