Due to such an unbalanced sex ratio, fierce sexual competition exists between and within red howler troops. Red howler males, which are expelled from their natal troop upon reaching sexual maturity, are forced to invade an outside group and gain admittance. Once they have accomplished this, they violently kill any infants present in the group. By killing infants in a newly invaded troop, a male can mate quickly and ensure that the new offspring of the group are his own. Mothers do try to protect their offspring against assaulting males. Unfortunately for the female, this is not particulaly successful; less than 25% of offspring survive a male howler invasion.
The mating behavior of red howlers is another interesting aspect of their social interactions. Males and females often form consortships, an unusually close spatial relationship, before any sexual exchange has begun. Once these associations are established, sexual solicitations begin. Although seductive behaviors can be performed by both sexes, the female most often takes on the aggressive role. When attempting to attract a male, the female approaches him and moves her tonque rhythmically. The male may respond the same way, but if he does not, the female may simply try to entice another male.
Mating System: polygynous
Alouatta seniculus appears to breed throughout the year. However, in two habitats in Venezuela, the birth frequency is reduced during the early wet season, May through July. The estrous cycle ranges from 16-20 days, with the female being receptive for 2-4 days. Red howler females give birth for the first time around 5 years of age, while males usually do not father an offspring until approximately 7 years. Therefore, a female reaches sexual maturity a couple of years before a male.
(MacDonald, 1985) (Nowak, 1991) (Smuts et. al, 1986)
Breeding season: Red howler monkeys breed year round
Average age at sexual or reproductive maturity (female): 5 years.
Average age at sexual or reproductive maturity (male): 7 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Average birth mass: 263 g.
Average gestation period: 190 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (female)
Sex: female: 1475 days.
Newborn A. seniculus are at first quite helpless and are carried around at the mother's belly. Young red howlers begin using their prehensile tails before they are one month old. An infant uses its tail to secure itself to its mother, for in this stage of its life the mother pays little or no attention to her offspring, and fails to give the baby any assistance!
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female); extended period of juvenile learning