Ring-tailed lemurs have an extremely short mating season; it has been described as being "brief and bloody" (Jolly 1985). The mating season occurs in April and lasts less than two weeks, and a single females is receptive to males for only one day out of the entire year (Chalmers 1980, Jolly 1985, Jolly 1988). The female estrous is very visible, during which the genetalia swell from 1.5 to 3 cm in length and develop a pink center (Jolly 1966). Synchronization of mating activities between sexes as well as synchronization of the menstrual cycles among females has been observed in many primate species (including humans), and the most extreme example of this is found in lemurs. All adult females in a number of adjacent groups were found to become receptive at the same time (Chalmers 1980, Jolly 1985). This synchrony of breeding is probably achieved through olfactory communication, since lemurs' several scent glands are used most extensively during the breeding season (Chalmers 1980). Female ring-tailed lemurs first give birth at 3 years of age, and will continously give birth every year following. Single births are most common, though the occurance of twins has been found when the female is in very good health and resources are abundant. Due to the synchronization of breeding activity, all infants in a troop are born within a matter of days (Haring 2004).