Menstruation (mammal)
Most female mammals have an estrous cycle, yet only ten primates species, four bats species, the elephant shrew, and the spiny mouse have a menstrual cycle. The relatedness of these groups suggests that four distinct evolutionary events have caused menstruation to arise.
Reproductive suppression
Yellow, banded and dwarf mongooses live in families similar to wolf packs with scent marking done almost exclusively by the dominant pair. Dwarf mongooses show synchronous estrous but only the dominant female regularly gives birth. Subordinate females do not conceive or abort early, but do lactate after the dominant female gives birth and participate in communal nursing. When the subordinate females leave the parental pack they will become fully reproductively active in new groups they help establish. In captivity more than one dwarf mongoose in a group can give birth but the young of subordinates do not survive. However, if the size of their cage is increased and density is lower, reproductive activity of subordinates resumes. As in wolves, pheromonal control over the reproductive cycle of the mongoose is implicated as the mechanism for reproductive suppression.
The house mouse ("Mus musculus") is territorial with a single dominant male marking its territorial boundary with urine while subordinate males do not urine mark. A female's rate of urine marking is elevated in response to a dominant male's urine marking, and his urine contains pheromones that accelerate her ovulation. The presence of a dominant adult male and his urine are crucial for young females to initiate puberty. Females isolated from males often do not experience puberty or have unstable ovulatory cycles. Contact with the urine of a dominant female signals a young prepubescent female to delay the onset of puberty. When housed with only an adult male, female mice reach puberty within 25 days, but puberty will not occur until 40–50 days if they are housed with adult females. Being grouped with other females suppresses the young female's serum LH and prolactin. Exposure to the male elevates their LH levels followed by increased serum estradiol. Female mice have a short ovulatory cycle when housed with males and a long cycle when housed with only other females.