Abstract # 3164 Poster # 170:

Scheduled for Sunday, September 18, 2011 07:00 PM-09:00 PM: Session 23 (Salon G (Sixth Floor)) Poster Presentation


BROTHERS IN ARMS: COALITION FORMATION BY FREE-RANGING MALE VERVET MONKEYS (CHLOROCEBUS AETHIOPS PYGERYTHRUS)

N. J. Freeman, J. Sashaw, L. Barrett and P. Henzi
University of Lethbridge, 4401 University Dr W, Lethbridge, Alberta T1K3M4, Canada
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While coalition formation by unrelated adult male primates is uncommon, those species in which it occurs provide data that are very valuable for our understanding of the evolution and maintenance of cooperation. Vervet monkeys live in female-philopatric troops that contain one or more non-natal, resident adult males. This multimale social organization presents the opportunity for males to form coalitions although this has not yet been reported for vervets. Here we present data on male coalitions obtained over the period January-December 2010 from two troops of vervet monkeys (NA=48, NB=72) living in South African semi-desert. We collected focal data on the male cohorts in these troops (NA=11, NB=16), supplemented by ad hoc observations, and recorded a total of 64 polyadic aggressive encounters among males in both troops. These constituted 3.6% of all male-male aggression, were predominantly triadic (85.9%) and occurred significantly more frequently during the three-month breeding season (CHI2=32; 1df, P<0.001), although this was when most male-male fighting took place. Where we observed the beginning of the encounter (N=40), we found that almost all (N=39) coalitions involved a male aiding the aggression initiator who was lower ranking than the target 64% of the time. Targets only retaliated on 13/64 occasions (20.3%) and were not more likely to do so if they were higher ranking than the initiator (CHI2=0.136, 1df, P=0.71, Yates correction applied).