Menstruation (mammal)
Menstruation in mammals is the shedding of the uterine lining (endometrium). It occurs on a regular basis in uninseminated sexually reproductive-age females of certain mammal species.
Hoover-Drickamer effect
A similar phenomenon of menstrual synchrony has been investigated multiple times to determine whether or not it even exists, and if it is adaptive in nature. The same cannot be said of variations in duration of estrus. The rationale behind investigations into menstrual synchrony could also be applied to duration of estrus, including male monopolization of fertile females. While one argument against menstrual synchrony is to reduce interfemale competition, particular differences between species in terms of mating period and length may influence how useful the ability to mediate and change estrus is in the first place. Given that mice can breed year round, it may be adaptive for females to be able to influence each other's frequency of sexual receptivity in order to increase the likelihood of overall species survival.