Squirrels are a familiar sight in many neighborhoods, darting through trees and foraging for nuts. Parental care is widespread across the animal kingdom, involving significant effort to raise offspring until independence. A question that arises is whether this care extends beyond biological offspring, specifically, do squirrels adopt orphaned young? This article will explore the scientific observations and factors that influence such behaviors in squirrels.
Understanding Squirrel Parental Care
Female squirrels typically bear one or two litters annually, with litter sizes ranging from two to eight offspring. They construct insulated nests, called dreys, often in tree cavities or branches, using materials like leaves, twigs, and fur. These nests provide a safe and warm environment for the vulnerable young.
Newborn squirrels are altricial, meaning they are born blind, deaf, and hairless. The mother squirrel suckles her young for several weeks, providing nutrient-rich milk. For grey squirrels, the gestation period is about 42 to 45 days, and the young are weaned around 10 to 12 weeks of age. Mothers are highly protective, aggressively defending their drey and offspring from potential threats.
Instances of Orphan Adoption
Squirrels have been observed to adopt orphaned young, a behavior that, while not extensively studied, has been documented by wildlife rehabilitators and researchers. For instance, a notable observation by University of California researchers involved a female Eastern gray squirrel adopting an orphaned baby from a nearby territory after its mother died. The adoptive mother integrated the orphan into her existing litter, nursing and caring for it alongside her own biological offspring until it reached independence.
Such adoptions have been reported for various squirrel species, including Eastern gray squirrels and red squirrels. While red squirrels are generally territorial and solitary, studies have shown they will adopt orphaned pups, though these instances are rare. Over two decades, one research project documented only five cases of adoption among thousands of litters, indicating it is an infrequent behavior.
Factors Influencing Adoption
Several factors influence whether a squirrel will adopt an orphan. Genetic relatedness plays a significant role, as squirrels are more likely to adopt if the orphans are closely related, such as nieces, nephews, siblings, or grandchildren. This behavior aligns with kin selection, an evolutionary concept where an individual’s altruistic actions benefit the survival of shared genes in relatives.
The costs and benefits of adoption are implicitly weighed by the adoptive mother. Squirrels tend to adopt when the costs of raising an additional young are low, and the genetic benefits from helping relatives are high. For example, a female with two pups might adopt a niece or nephew, but if she has three pups, she might only adopt a grandchild or younger sibling, as they share a higher percentage of genes. Proximity of the orphan to the potential adoptive mother’s nest can also be a factor, as it increases the likelihood of encounter and subsequent integration.