Lions have very high copulation rates. The female may mate approximately every 15 minutes when she is in heat for three days and nights without sleeping, and sometimes with five different males. This often leads to physical exhaustion of males when only a one or two are involved. Males periodically sniff female reproductive organs for signs of oncoming estrus and if these signs are detected, they will follow a female until she is ready to mate. Females may signal their interest in mating with elaborate tail movements and by "walking sinuously past" a male. "Oral sex" occurs as foreplay-female lions may lick and rub the male's genitals. When African lion female has gotten the male's attention, she crouches into the mating position, her belly pressed to the ground and tail to one side, and copulation occurs for five to twenty seconds. During mating males often bite the female at the nape of her neck and the act often ends with the female snarling with bared teeth at the male. The penis of a lion, like all felines, has backward pointing barbs. In lions, copulation is often accompanied by snarling, biting, growling, and threats, and sometimes the female turns and swats the male during dismount (most likely as a result of the pain invoked by a barbed penis). It has been theorized that the pain inflicted upon the female, during withdrawal from her vagina, is neccesary to stimilate the female to ovulate. After a new group of males take over a pride, females usually increase their sexual activity while lowering their fertility rate.
For every cub that survives to yearling stage, lions copulate an estimated 3000 times. Only 1 estrus in 5 results in progeny and estrus lasts 4 days to a week, during which couples mate 2.2 times/hour. Either animal will initiate mating by rubbing heads or sniffing. The two literally sleep, mate, sleep, mate, sleep and mate again during this time. If females fail to conceive they will re-enter estrus approximately two weeks later and the cycle begins anew. The couple may mate hundreds of times over several days, but afterward, when they return to the pride, they show no special interest in each other. Surprisingly, coalition partners hardly ever fight over mating rights. The first to reach a female in heat becomes her consort—until and unless he has had enough. As partners are usually equals, fighting would impair their ability to withstand takeover attempts.
When a male cat opens his mouth and wrinkles his nose, it may mean he smells a receptive female. By smelling through a special organ in the roof of its mouth, a male cat senses when a female is ready to mate. This behavior is called flehmen. The special organ (the Jacobson's organ) is located just behind the front teeth and above the roof of the mouth. Two tiny openings in the palate allow the scented air to reach it. Nerves then carry the news to the olfactory part of the brain, where the scent is recognized. Domestic cats often demonstrate the same behavior when sniffing a territorial scent mark -- or sometimes when smelling catnip!