Abstract # 2144 Event # 191:

Scheduled for Saturday, June 23, 2007 11:45 AM-12:05 PM: Session 18 (North Main Hall C/D) Symposium

Marmosets: Cooperative Breeders or Fierce Competitors?

L. J. Digby
Biological Anthropology and Anatomy, Duke University, Durham, NC 27701, USA
     In 1990, I was the co-winner of the ASP Student Poster Award for a presentation entitled “An experimental test of dispersal choices in Callithrix jacchus"  where I described that female subjects did not try to avoid unfamiliar cycling females. At the time, there was some question about whether common marmosets, known for reproductive suppression in subordinate females, would be characterized as monogamous or possibly polyandrous. In subsequent years, I initiated a field site for the study of marmoset mating patterns and infant care behavior in northeastern Brazil in conjunction with the Federal University of Rio Grande do Norte. Based on over 2500 hours of focal and scan samples, we observed over 100 mounts and copulations and the presence of two breeding females in multiple groups. Mating patterns could be described as a combination of monogamy and polygyny with high levels of extra-group copulations. The observation of an infanticide, most likely by the dominant female of the group, has sparked a new line of research into levels of reproductive competition in cooperative breeders. Using comparative studies, we argue that cooperative breeding, with its inherently high levels of reproductive skew, gives rise to extreme levels of reproductive competition.