North American tree squirrels exhibit a highly specialized division of labor that challenges the expectation of shared parental duties. The roles of the male and female are distinct, particularly concerning the construction of their homes and the care of their young. For the male squirrel, his contribution to the family unit ends shortly after mating, leaving the entire responsibility of nest building and parental duties to the female. This solitary approach to reproduction is a defining characteristic of these widespread rodents.
Understanding the Squirrel Home
Tree squirrels, such as the Gray and Fox squirrels, utilize two primary types of shelters: the drey and the tree cavity. A drey is a spherical nest constructed in the branches of a tree, often tucked into a crotch or near the trunk for stability. These structures are built from a framework of interwoven twigs and branches, forming a messy-looking ball about the size of a football. The drey functions as a temporary or seasonal shelter for sleeping and resting.
A tree cavity, or den, is a natural hollow within a tree trunk or large limb, sometimes created by woodpeckers or through natural decay. These dens are highly sought after because they offer superior protection from predators and severe weather. The cavity is typically lined with soft materials to create a comfortable interior. Both dreys and cavities provide necessary refuge, but their use often shifts depending on the season and the squirrel’s immediate needs.
The Female’s Exclusive Role in Nest Construction
The female squirrel is the sole architect and maintenance worker for the nursery nest, a structure that must be robust enough to protect her altricial young. For gestation and early rearing, she will either heavily fortify an existing cavity den or build a specialized, insulated drey. This maternity nest is considerably more complex and durable than a simple sleeping drey.
The construction process begins with gathering coarse materials like small branches and twigs to form the outer shell and foundation. She strategically weaves these components together, often incorporating damp leaves and moss to create a more stable, weather-resistant structure. The core of the nest is a hollow sphere, roughly 30 centimeters in diameter, which she meticulously lines.
The inner lining is made of fine, soft materials, including shredded bark, grass, pine needles, and moss. These materials provide insulation and cushioning for the litter. This robust, multi-layered structure is designed to retain heat and shield the vulnerable, blind, and naked newborns, or kits, which are born after a gestation period of about 42 to 45 days. A female will often build multiple nests, maintaining several as backups in case a primary nest is disturbed by a predator or becomes infested with parasites.
Why Male Squirrels Are Not Co-Parents
Male squirrels are characterized by a solitary and polygynous mating system, meaning they seek to mate with multiple females and form no lasting pair bonds. Once the mating chase is complete and the female is successfully inseminated, the male’s reproductive role is finished. He exhibits no paternal instincts and makes no investment in the subsequent care of the young or the construction of the nursery.
The female is entirely responsible for the six to ten weeks of nursing, protecting, and teaching the kits necessary survival skills. Male and female squirrels will occasionally share a nest for brief periods, such as during intense cold snaps to conserve body heat, but this cohabitation is not related to co-parenting. The male does not share the nursery nest with the pregnant or nursing female, ensuring the family unit functions as a single-parent home.
The energy and time a male dedicates post-mating are instead focused on foraging for his own survival and competing with other males for future mating opportunities. This lack of paternal involvement is typical among many rodent species and is an evolutionary strategy where the male’s fitness is maximized by seeking more mates rather than investing in the current litter.