Differentiating between male and female squirrels from a distance can be difficult, as species like the Eastern Gray or Fox Squirrels exhibit limited sexual dimorphism in size and coloration. Both sexes appear similar, meaning external physical characteristics are often the only reliable indicators for field observation. A non-invasive approach relies on observing specific anatomical details when the animal is still, interpreting certain social actions, and considering the time of year to provide circumstantial evidence. Identifying sex relies on a combination of subtle observations.
Direct Visual Cues
The most definitive, though often challenging, way to determine a squirrel’s sex is by observing the anogenital region beneath the tail. This requires the animal to be stationary and positioned so its underside is visible, such as when climbing a tree trunk or sitting upright. In male squirrels, the distance between the anus and the genital opening, known as the anogenital distance, is noticeably longer. The male’s scrotum, containing the testes, is located further away from the anal aperture.
The scrotum’s visibility fluctuates seasonally, becoming more prominent and sometimes swollen during the breeding periods, which aids in identification. Conversely, a female squirrel’s corresponding openings are located very close together, appearing as a single, small opening immediately under the tail. Females also possess teats or nipples, typically four pairs, along their abdomen. These mammary glands are usually difficult to spot unless the female is actively nursing, causing the teats to become enlarged and more visible.
Behavioral Indicators
Specific social interactions, particularly during the reproductive period, offer strong clues to a squirrel’s sex. The most obvious is the characteristic “mating chase” that occurs when a female is in estrus and receptive to mating. This event involves one female being pursued by a group of multiple male squirrels.
The female is the individual being chased, while the males are actively following and competing for access. Males exhibit increased aggression toward each other during these times, often engaging in wrestling, chasing, and vocal threats to establish dominance. Furthermore, males may engage in scent-marking behaviors, such as rubbing their cheeks and glands on branches or trees, to advertise their presence and territory to rivals. The squirrel that consistently pursues others during this ritual is almost certainly a male, while the one being followed is the female.
Contextual Observation
A squirrel’s activities tied to the annual reproductive cycle offer compelling circumstantial evidence of its sex. Eastern Gray squirrels typically have two breeding seasons each year, with peaks occurring in late winter or early spring and again in mid-summer. Observing a squirrel carrying large amounts of nesting material, such as leaves or twigs, into a drey (nest) is a strong indication of a female preparing to give birth.
Female squirrels are solely responsible for constructing and maintaining the natal drey, taking on all parental duties without male assistance. Seeing a squirrel consistently entering and exiting a nest site, especially during the expected birthing periods, suggests it is the mother. A female may also be seen aggressively defending a specific drey from intruders, as they are highly protective of their young. Any squirrel observed actively nursing young or exhibiting solitary care of a nest is reliably identified as a female.