Squirrels are adaptable mammals found across various environments, from dense forests to urban parks. Beyond their visible presence, squirrels play a part in their ecosystems, notably through seed dispersal, as they frequently bury nuts and acorns, some of which later sprout into new trees.
Typical Litter Size and Frequency
The number of offspring squirrels have per litter, known as kits or pups, varies depending on the species and environmental conditions. Eastern Gray Squirrels (Sciurus carolinensis) typically have litters averaging two to four babies, though this can range from one to eight. Litters born in the summer tend to be larger than those born in late winter. American Red Squirrels (Tamiasciurus hudsonicus), which are smaller, usually produce an average of four young, with a typical range of one to five kits, though litters can reach up to seven.
Most squirrels have two litters per year. Eastern Gray Squirrels commonly follow this pattern, with one litter in late winter or early spring and another in late summer. The success and frequency of breeding are influenced by factors like food availability and habitat quality. A plentiful supply of food can contribute to earlier and more successful breeding seasons, and a small percentage of gray squirrels may even have a third litter during years with mild weather and abundant food. In contrast, American Red Squirrels typically have only one litter annually, though they may have two under favorable conditions.
The Squirrel Breeding Cycle
Squirrel reproduction typically occurs during two main periods each year. For Eastern Gray Squirrels, the first breeding season often begins in late December or early January, leading to births in early spring, usually between February and April. A second breeding period for gray squirrels occurs from late June through August, with offspring typically arriving in late summer or early fall. Red squirrels have a somewhat different schedule, with their breeding season generally peaking from March to August.
Environmental factors, such as food availability and climate, play a role in determining the timing and success of these breeding periods. Mild winters, for example, can lead to an earlier start of the mating season. Female squirrels are polyoestrous, meaning they have multiple ovulation cycles annually, and are receptive for only a single day during each cycle. During the mating period, males often engage in “mating chases,” pursuing the female through trees.
The gestation period for Eastern Gray Squirrels is typically between 40 and 44 days. For American Red Squirrels, the gestation period ranges from 31 to 35 days.
Raising the Young
After a gestation period, squirrel kits are born in a drey, a sturdy nest built by the female. These young are altricial, meaning they are born blind, deaf, and hairless, making them completely dependent on their mother for care. Eastern Gray Squirrel kits weigh approximately 14-18 grams at birth, while red squirrel kits are generally between 10 and 18 grams. The mother alone is responsible for raising the young; males do not participate in their care.
During the first few weeks, the kits remain in the nest, nursing frequently. Their skin begins to darken and fur appears around two to three weeks of age, with full fur development by around four to five weeks. Eyes and ears typically open at about four to five weeks old.
Young squirrels begin to venture outside the drey at six to seven weeks of age, at which point they also start to consume solid food. Weaning from the mother’s milk usually occurs around 10 to 12 weeks of age, by which time they are nearly adult size and becoming independent. The mother continues to teach them survival skills, such as foraging and navigating their environment, before they become fully independent.