Most species of squirrels -- rodents that inhabit various regions across the globe -- can be grouped as tree or ground squirrels. Information about each group’s behaviors and physical traits provides insight needed to determine whether the squirrel of that group is male or female. The sex of a squirrel is difficult to determine if attempting to go by obvious physical characteristics, because male and female squirrels are usually of the same size, shape and color.

Both male and female squirrels are communal, interacting with other squirrels within their immediate living area. However, the nesting habits of male and female tree squirrels differ. Males can be observed nesting together during winter months. It is uncommon for some female tree squirrels, such as fox squirrels, to nest together. An adult squirrel observed interacting with a litter is likely to be the mother of the litter. Male squirrels of any kind do not participate in the rearing process.

Female ground squirrels emerge from hibernation later than their male counterparts. For this reason, ground squirrels observed the soonest after a hibernation period are more likely to be male. Juvenile ground squirrel males exhibit much more movement, exploration and boldness compared to juvenile females. In accordance with this increased movement and exploration, all male juvenile ground squirrels leave the area in which they are born by the time they are one year old. Female ground squirrels stay near the burrows they were born in and form communes with other related females.

The squirrel mating ritual involves a single male or multiple males chasing a female. The males also compete with each other by chasing each other. The most dominant male is the one who typically mates with the female first. The female will sometimes mate with additional suitors afterwards. For some species of tree squirrels, the mating window is so short that the female only remains in estrus, the period of time when pregnancy is possible, for a few hours.

Certain telltale traits of male and female squirrels emerge during the mating season. The scrotum of male squirrels becomes visible because it enlarges and descends. During non-mating periods, the testes are withdrawn into the body. The nipples of adult female squirrels become more prominent during the mating season. The location of the genitals differs between male and female squirrels. The male reproductive organs are located closer to the navel, while the females' are located closer to the anus.

To prevent injury to themselves or the rodents, people should avoid attempting to handle wild squirrels. Feeding squirrels with human food or even a squirrel feeder is discouraged for several reasons. These reasons include accidentally providing food for invasive species, diminishing squirrels' protective fear of humans or providing unhealthy food to the squirrels.