In mammals, except primates, heat condition develops in

Estrous cycle, or oestrous cycle, is the reproductive cycle found in most mammalian placental females, whereby there are recurring periods when the female is fertile and sexually receptive (estrus) interrupted by periods in which the female is not fertile and not sexually receptive (anestrus). Animals that have estrous cycles reabsorb the endometrium (inner membrane of the mammalian uterus) if conception does not occur during that cycle. During the estrous period also known as heat period, mature eggs are released from the ovaries.