Abstract # 202:

Scheduled for Saturday, June 22, 2013 11:00 AM-11:15 AM: Session 24 (Auditorium) Oral Presentation


T. Gregory1 and M. Bowler2
1Smithsonian Conservation Biology Institute, National Zoological Park, 1100 Jefferson Dr., SW, MRC 705, Suite 3123, Washington, DC 20013, USA, 2San Diego Zoo Global Institute for Conservation Research, Escondido, CA 92027

Cacajao and Chiropotes distinguish themselves from other platyrrhines because of their extreme specialization for seed predation, massive home ranges, and unique social systems. These two genera form groups larger than most other platyrrhines (Cacajao: 200+ and Chiropotes: <80 individuals), with relatively high proportions of adult males. Groups move rapidly through the high canopy and group membership is highly dynamic, with group size changing both daily and seasonally. In both genera, males engage in highly affiliative, sex-specific behaviors, at times during formation of all-male subgroups. Curiously, both genera also have very conspicuous genitalia and demonstrate sexual crypsis, or potential sexual mimicry, wherein testes are retracted, resembling labia. Observed egalitarian interactions amongst Chiropotes males suggest that there is scramble competition for access to females, while observation of aggressive inter-troop encounters indicates high intergroup competition. As of yet, there are no genetic data to explain dispersal patterns, and while relatedness amongst males would in part explain their affiliative relationships, there is some limited evidence for dispersal by males in Cacajao. Nonetheless, the ability to maintain large groups in these genera may be related to the affiliative and perhaps coalitionary relationships between males. Affiliative male-male relationships may allow for monopolization of groups of females and facilitate group cohesion by reducing intragroup aggression, which in turn enables large group sizes, high mobility, and exploitation of widely dispersed resources like seeds.