Brown howlers form multi-male, multi-female groups; single-male, multi-female groups; and single-male, single-female groups. The most common group composition is single-male, multi-female with up to 10 individuals. The alpha male usually monopolizes all reproductive females and sires all young. In Primates where males outnumber females, male-male competition for resources and mates is intense, which may lead to sexual dimorphism and polygny. Adult males disperse from their natal group and must compete with alpha males to gain acceptance into a new social group.
Extra group copulations are less frequent in Alouatta relative to other Primates. After male solicitation, the female moves towards the male and performs rhythmic tongue movements. Shortly after, copulation takes place and lasts about one minute. Sometimes genital inspection also occurs. Often, female brown howlers initiate extra-group copulations and are more prone to do so in multi-male groups. Members of the female's group are indifferent to any extra group copulations that she may perform.
Mating System: monogamous ; polyandrous ; polygynous ; polygynandrous (promiscuous)
Brown howlers are year-round breeders. Their folivorous diet may account for the ability to breed year-round, as mature leaves are available throughout the year and provide a relatively stable source of energy. Rubbing behavior is well documented in several members of Primates and serves multiple functions. Adult male brown howlers exhibit extreme rubbing behavior as a marker of dominance and reproductive status. Status-based differences in rubbing behavior are also observed among female brown howlers. Rubbing plays an important role in intersexual and intrasexual dominance interactions and in aggressive and territorial behavior. Females reach adulthood at approximately 3.6 years and males at approximately 5 years.
Breeding interval: Females can breed once every 22 months
Breeding season: Brown howlers are year-round breeders
Average number of offspring: 1.
Average gestation period: 6 months.
Average weaning age: 12 months.
Average age at sexual or reproductive maturity (female): 43 months.
Average age at sexual or reproductive maturity (male): 61 months.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Like most primates, brown howlers have altricial young with extended periods of juvenile development. As is the case with most polygynous species, maternal investment is high in this species. Gestation last for approximately 6 months and young are usually weaned by 1 year old. Young begin to explore their environment independent of their mother at five months old. Males exhibit minimal paternal investment, and allomaternal care is rare in brown howlers.
Parental Investment: altricial ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female); post-independence association with parents; extended period of juvenile learning