estrus, also spelled Oestrus, the period in the sexual cycle of female mammals, except the higher primates, during which they are in heat—i.e., ready to accept a male and to mate. One or more periods of estrus may occur during the breeding season of a species.

Do primates experience estrus?

Evolution. Most female mammals have an estrous cycle, yet only ten primate species, four bats species, the elephant shrew, and one known species of spiny mouse have a menstrual cycle. As these groups are not closely related, it is likely that four distinct evolutionary events have caused menstruation to arise.

Do humans have an estrous cycle?

Humans have menstrual cycles rather than oestrous cycles. They, unlike most other species, have concealed ovulation, a lack of obvious external signs to signal estral receptivity at ovulation (i.e., the ability to become pregnant).