Mantled Howler - Reproduction

Reproduction

The mantled howler uses a polygamous mating system in which one male mates with multiple females. Usually, the alpha male monopolises the breeding opportunities, but if the alpha male is distracted, a lower-ranking male can get an opportunity to mate. And in some groups, lower-ranking males do get regular mating opportunities and do sire offspring. Alpha males generally maintain their status for about 2½ to 3 years, during which time they may father 18 or so infants. Females become sexually mature at 36 months, males at 42 months. Females reaching sexual maturity are typically 42 months old by their first birth. They undergo a regular estrus cycle, with an average duration of 16.3 days, and display sexual skin changes, particularly swelling and color change (from white to light pink) of the labia minora. The copulatory sequence begins when a receptive female approaches a male and engages in rhythmic tongue flicking. The male responds with the same tongue movements before the female turns while elevating her rump, which allows for mating to begin. Females apparently also use chemical signals, since males smell the females' genitals and taste their urine. The gestational period is 186 days; births can occur at any time of year. The infant's fur is silver at birth, but turns pale or gold after a few days. After that, the fur starts to darken, and the infant takes on the adult coloration at about 3 months old.

The infant is carried under its mother, clinging to its mother's chest, for the first 2 or 3 weeks of its life. After that, it is carried on its mother's back. At about 3 months the mother will usually start to push the infant off, but will still carry the infant some of the time until it is 4 or 5 months old. After the young can move on its own, the mother will carry it across difficult gaps in the trees. Juveniles play among themselves much of the time. Infants are weaned at 1½ years old at which point maternal care ends. Adult females typically give birth every 19 to 23 months, assuming the prior infant survived to weaning.

The mantled howler differs from other howler monkey species in that the males' testes do not descend until they reach sexual maturity. Upon reaching sexual maturity, the young monkeys are usually evicted from their natal group, although the offspring of a high-ranking female may get to stay in its natal group. However, many infants do not reach sexual maturity; high-ranking adults sometimes harass or kill the offspring of lower-ranking monkeys to eliminate competition to their own offspring for an opportunity to remain with the group upon reaching maturity. Natal emigration is performed by both sexes, with 79% of all males and 96% of the females leaving their original social group. When a male from outside the group ousts the previous alpha male, he normally kills any infants so that the mothers come into estrus quickly and are able to mate with him. Predators such as cats, weasels, snakes and eagles also kill infants. As a result, only about 30% of mantled howler infants live more than one year. The highest reproductive success occurs in the middle-ranking females, with the alpha position lower possibly because of competitive pressures, and infant mortality appears to be lower when the timing of births in a group of females is clustered. If it survives infancy, the mantled howler's lifespan is typically 25 years.