Los Amigos;single-species study;small spatial scales;animal behavior;animals;primates;Callicebus brunneus;sexual selection
Close male-female bonds in primates are thought to relate to three categories of sex-specific benefits: joint resource defense, male mating exclusivity, and the delivery of male services that increase female reproductive success. In addition to documenting the natural history of brown titi monkeys (Callicebus brunneus) at Los Amigos Research Center in Amazonian Peru, this thesis explores these three potential benefits by examining the bonds between pairmates of C. brunneus, a predominantly frugivorous species characterized by strong attraction between the pairmates in each group. I studied seven sets of pairmates in a Peruvian rainforest, using observational sampling and playbacks of unfamiliar calls (simulating intruders) to quantify behavioral indicators of pair-bondedness that have been suggested by studies of captive titi monkeys. I correlated changes in these behavioral indicators with differences in the physical environment (fruit abundance, territory location) and social environment (proximity of a sexual competitor to the subject’s pairmate). Both males and females exhibited more affiliative and arousal behaviors in the presence of real or simulated intruders than in their absence. This thesis presents suggestive evidence that male investment in the pair bond reflects a mixed reproductive strategy of direct mate defense via mate guarding and indirect mate defense via resource defense, and female investment reflects a similarly mixed strategy of resource defense and, to a lesser degree, mate defense. The multiple proposed pair bond functions highlight the importance of considering both cooperative and conflicting male and female reproductive interests.