Abstract # 259:

Scheduled for Saturday, June 20, 2015 02:15 PM-02:30 PM: (Cascade H) Oral Presentation


LOW-LEVEL VERSUS SERIOUS AGGRESSION IN FOOD RESOURCE AND NON-FOOD RESOURCE CONTEXTS AND GROUP STABILITY IN CAPTIVE RHESUS MACAQUES (MACACA MULATTA)

D. Hannibal1, B. Beisner1,2, A. Nathman1 and B. McCowan1,2
1California National Primate Research Center, UC Davis, Davis, CA 95616, USA, 2Department of Population Health & Reproduction, UC Davis, Davis, CA, 95616 USA
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     Matriline relatedness can decrease over time, resulting in fragmentation that is associated with social instability and serious aggression in rhesus macaques. We assessed whether experimental removal of matriline fragments (N=18 individuals) to increase relatedness was associated with reduced serious aggression and whether this varied by context (food resource versus other). Conflict event data among 103 subjects aged 3 to 29 from a captive rhesus group were recorded during a 7 week pre-removal, 7 week post-removal, and 7 week follow-up phases from March through July 2013. Events were categorized as either low level aggression (threats, pushes, short chases) versus more intense contact aggression (long chases, wrestling, pinning, and biting). We fit a mixed-effects binomial regression model of aggression frequency per individual per study phase (N=18896 records). The best fit model showed that the probability of serious aggression during an event did not change between pre-removal and post-removal phases (post vs. pre: Beta=0.07, p=0.16), but decreased in the follow-up phase (follow-up vs. pre: Beta=-0.15, p=0.009). An interaction of context and dominance certainty showed individuals with more certain dominance used more serious aggression in non-food contexts (dominance certainty: Beta=0.93, p<0.001; food vs. other context: Beta=0.05, p=0.88; dominance certainty × food: Beta=-1.08, p=0.002), but not in food contexts. This suggests that in stable groups, food contexts will have more low-level aggression associated with maintaining stable relationships.