A squirrel's gestation period is between 30 and 44 days. Squirrels typically have one or two litters a year, depending on the type of squirrel.
Fox squirrels and Eastern grey squirrels have two litters a year with their young being born between February and April for the first litter and between August and September for the second. Western grey squirrels have one litter a year, typically with their young being born between February and June. Baby squirrels are born without hair and are mostly helpless for the first months of their lives. A squirrel's nest, typically built of twigs, is called a drey.