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.
Animal sexual behaviour
When animal sexual behaviour is reproductively motivated, it is often termed "mating" or "copulation"; for most non-human mammals, mating and copulation occur at oestrus (the most fertile period in the mammalian female's reproductive cycle), which increases the chances of successful impregnation. Some animal sexual behaviour involves competition, sometimes fighting, between multiple males. Females often select males for mating only if they appear strong and able to protect themselves. The male that wins a fight may also have the chance to mate with a larger number of females and will therefore pass on his genes to their offspring.