The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

The single life: Physical injuries may reflect the costs of being a solitary owl monkey


1Anthropology, University of Pennsylvania, 2Fundación E.C.O, Cecoal-Conicet, 3Biological and Forensic Sciences, University of Derby, 4Anthropology, University of Texas at Austin, 5Anthropology, Yale University

March 26, 2015 , Archview Ballroom Add to calendar

Azara’s owl monkeys (Aotus azarae) are socially and genetically monogamous, territorial primates in which offspring of both sexes disperse from their natal groups. After dispersing, individuals range solitarily for a period ranging from a few days to many months. Understanding the behavior and physiology of individuals during the solitary life history stage is relevant for illuminating the evolution and maintenance of serial monogamy observed in this species. While dispersing earlier may allow individuals to maximize their reproductive life spans if they establish themselves as reproductive adults sooner, it may also carry costs. We predict that solitary subadults will be smaller, lighter, show fewer signs of adult development (e.g. gland secretions), and more frequently have scars, torn ears, and other signs of injuries indicative of intraspecific fighting than similarly aged, predispersing, subadults. As part of the Owl Monkey Project in Formosa, Argentina, we collected morphometric data from 62 subadults (aged 24-48 months) captured between 1999 and 2014. Differences in weight, body length, or gland development between solitaries and subadults in social groups did not reach statistical significance. However, a greater proportion of solitaries showed signs of injuries than predispersing subadults (69% versus 23%, Fisher’s Exact Test: odds ratio=0.133, CI=0.02-0.59). While our results do not support the idea that dispersing early carries costs in terms of growth or development, solitaries do seem to face higher rates of injuries. Ongoing studies characterizing hormonal levels of solitaries and examining encounters between solitaries and social groups will further elucidate the potential costs of early dispersal.

Funding provided by the National Science Foundation (BCS-6400621020, BCS-837921, BCS-904867, BCS-924352), National Institutes of Aging, Wenner-Gren Foundation, Leakey Foundation, and National Geographic Society.