Abstract # 201:

Scheduled for Monday, September 19, 2011 08:30 AM-08:45 AM: Session 25 (Meeting Room 408) Oral Presentation


A. Link1,2,3,4 and A. Di Fiore1,2,3
1New York University, 25 Waverly Place, New York, NY 10003, USA, 2New York consortium for Evolutionary Primatology, 3University of Texas at Austin, 4Universidad de Los Andes
     Spider monkeys and chimpanzees are the only primates – apart from humans – where males participate in coalitionary aggression directed towards neighboring rival males. From 2005 to 2010 we studied intergroup relations in spider monkeys at a pristine rainforest in western Amazonia, recording data on 28 events associated with intergroup competition. These involved direct intergroup encounters (N = 12) as well as coordinated territorial boundary patrols and deep incursions into rival territories (N = 21). Only males initiated aggressive behavior during conflicts between groups. The number of males in a subgroup was the most influential socioecological variable triggering the initiation of territorial boundary patrols in spider monkeys. To date we have recorded all behaviors that Wrangham (1999) proposed to be associated with lethal coalitionary intergroup aggression in chimpanzees, apart from coalitionary kills. However, three out of 8 adult males from our primary study group disappeared during a season of peak intergroup conflict, and on two occasions we witnessed severe wounds inflicted on males that participated in intergroup fights. As noted for chimpanzees, among spider monkeys an “imbalance of power” seems to strongly influence the outcome of intergroup encounters. Spider monkeys provide a valuable and phylogenetically independent model with which to evaluate the basic principles underlying the expression of coalitionary intergroup aggression by males in human and non-human primates.