Patterns of aggression in spider monkeys (Ateles geoffroyii yucatanensis) at Runway Creek Nature Reserve, Belize
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“Patterns of aggression in spider monkeys (Ateles geoffroyii yucatanensis) at Runway Creek Nature Reserve, Belize” K. Hartwell¹, H. Notman1, 2, & M.S.M. Pavelka¹ ¹University of Calgary, Calgary, Alberta, Canada ²Athabasca University, Alberta, Canada Presenter’s Email: firstname.lastname@example.org A number of studies looking at aggression in Ateles describe high rates of both male aggression directed at females (female-directed aggression by males, or M-FDA), as well as female aggression toward other females (or F-FDA). M-FDA may be an expression of feeding competition, direct sexual coercion, or indirect sexual coercion, and F-FDA may function to limit scramble competition. We collected detailed data on all observed incidences of aggression (N=193) in two spider monkey communities between January 2008 and August 2011. Of these, 154 were instances of M-FDA, and 29 incidents were F-FDA. Oneway ANOVA shows that adult and subadult males are significantly more likely to initiate aggression, and that subadult females are the most common targets. In instances of F-FDA, subadult females were the targets in 53% of the cases. Nonparametric tests show that contexts of aggression differed between M-FDA and F-FDA; M-FDA occurred most often during subgroup fusions (males joining subgroups containing females who were not feeding) and during feeding (37% and 31% respectively, N = 154); in contrast, F-FDA aggression rarely occurred during fusions but was more likely during feeding (14% and 41% respectively, N=29). Our results support the hypothesis that M-FDA is a form of indirect sexual coercion, and as a result may encourage sexual segregation as females try to avoid potentially aggressive males.