Primates are typically considered microsmatic (i.e., having a relatively less developed sense of smell) when compared to other mammals, yet it is becoming increasingly clear that olfaction is an important sense involved in communication in numerous primate taxa, including humans. Still, compared to other social and mating systems, little is known about olfactory communication in strictly monogamous non-human primates. Here, a comprehensive approach using chemical, behavioral, and hormonal data is used to explore how putative olfactory signals may mediate the formation and maintenance of the social and sexual relationship between mates in a socially and genetically monogamous New World primate, the owl monkey (Aotus spp.). This dissertation couples data collected from a captive population of A. nancymaae, and from a wild population of A. azarae as part of the Owl Monkey Project, a long-term project in Formosa, Argentina. Chapter 2 includes a robust chemical analysis of volatile components in the glandular secretions of captive and wild owl monkeys, and identified sex, age, gland of origin, and possibly individual identity as biologically relevant information encoded in these secretions. Chapter 3 investigates potential chemosignals of relatedness. Captive owl monkeys differentially responded to odors based on the relatedness to scent-donor, suggesting a chemosignal of relatedness. Wild pairs showed greater estimates of genetic relatedness than expected with random mating, suggesting individuals in this population do not avoid inbreeding, and likely use some mechanism to recognize kin. Chapter 4 explores female fecundity as a potential chemosignal. Captive males discriminated between the reproductive phases of females using olfactory cues alone. However, behavioral and olfactory behaviors of both captive and wild breeding pairs showed these cues are of limited significance. Finally, chapter 5 takes a broader perspective, considering the role of sexual selection on olfactory communication in owl monkeys. Owl monkey olfactory traits are dimorphic, and this, coupled with the potential role chemosignals may play in reproduction and mate choice, suggest sexual selection has influenced chemical communication in owl monkeys. Still, the degree of dimorphism is reduced compared to other primates. This dissertation expands our knowledge of how olfactory communication may vary with social and mating patterns
