Squirrels follow a predictable annual reproductive cycle, known as their breeding season. Understanding this period helps in observing their behaviors and population patterns, as it involves specific mating times leading to the birth and raising of new generations.
Typical Breeding Periods
Most North American squirrel species, including Eastern Gray, Fox, and Red Squirrels, typically have two main breeding periods annually. For Eastern Gray Squirrels, the first period often begins in mid-winter (December-February), with a second around May to June. This allows young to be born in early spring and again in late summer. Fox Squirrels follow a similar pattern, with mating seasons in early winter and late spring.
Red Squirrels generally have their primary mating season in late winter or early spring (February-March). A second breeding period can occur in summer (June-July). While Eastern Gray and Fox Squirrels often produce two litters per year, some Red Squirrels, and younger females of any species, may only have one litter during their first reproductive year.
Influences on Breeding Timing
Several factors influence the timing and success of squirrel breeding seasons. Geographic location plays a role; squirrels in warmer climates may start breeding earlier or have more extended periods. Conversely, those in northern regions with harsher winters might limit themselves to a single breeding season due to higher energy demands.
Food availability significantly influences breeding frequency and success. Abundant nuts and seeds (mast crops) can lead to earlier breeding. Plentiful resources allow females to achieve the necessary body condition to reproduce, sometimes enabling two litters within a single year. If food is scarce, breeding may be delayed or reduced to only one litter.
From Mating to Raising Young
The breeding season encompasses events from courtship to the initial care of the young. When a female is receptive, she releases pheromones that attract males. Multiple males often engage in a competitive chase, pursuing the female through trees and across the ground, with the dominant male typically gaining mating opportunities. Females are receptive for a very short period, often less than a day.
After mating, gestation varies by species, generally ranging from 31 to 45 days. Eastern Gray and Fox Squirrels typically have a 40-45 day gestation, while Red Squirrels average 31-40 days. Litters are born in tree cavities or leaf nests constructed by the female; males do not participate in raising the young. Litter sizes vary from two to eight, with three to four common for Eastern Gray and Fox Squirrels, and three to seven for Red Squirrels.
At birth, squirrel pups (also called kittens) are altricial, meaning they are born hairless, blind, and deaf. They are entirely dependent on their mother for care and nourishment. Pups begin to develop fur around three to four weeks, and their eyes and ears open shortly thereafter. They typically start venturing outside the nest around six to eight weeks and are fully weaned by eight to twelve weeks, transitioning to solid foods.