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Reproduction and life cycle

Females reach sexual maturity at the age of 18 months to three years and are in estrus for about eight days of a 23-day cycle; the gestation period is approximately 91 days. Both adult males and females may mate with multiple partners, and a female's litter can have multiple paternities. Copulation is brief but frequent. Chronic stress can result in low reproductive rates in captivity as well as in the field.

Gestation is 82–103 days long. Only females are involved in parenting. Litter size is between one and six cubs, typically two. Caves and other alcoves that offer protection are used as litter dens. Born blind, cubs are completely dependent on their mother at first and begin to be weaned at around three months of age. As they grow, they go out on forays with their mother, first visiting kill sites and, after six months, beginning to hunt small prey on their own. Kitten survival rates are just over one per litter.

Juveniles remain with their mothers for one to two years. When a female reaches estrous again, her offspring must disperse or the male will kill them. Males tend to disperse further than females. One study has shown a high mortality rate among cougars that travel farthest from their maternal range, often due to conflicts with other cougars. In a study area in New Mexico, males dispersed farther than females, traversed large expanses of non-cougar habitat and were probably most responsible for nuclear gene flow between habitat patches.

Life expectancy in the wild is reported at 8 to 13 years and probably averages 8 to 10; a female of at least 18 years was reported killed by hunters on Vancouver Island. Cougars may live as long as 20 years in captivity. Causes of death in the wild include disability and disease, competition with other cougars, starvation, accidents, and, where allowed, hunting. The feline immunodeficiency virus is well-adapted to the cougar.