Genital Wounding in Chimpanzees (Pan troglodytes): Targeted Attacks or Happenstance?

Abstract

Reports of primate violence frequently note wounds to the genital region, raising the possibility that attackers target genitals to eliminate the reproductive capacity of rivals. Alternatively, in chimpanzees (Pan troglodytes) and other species with prominent genitals, injuries may occur simply because large size makes genitals easy targets. To test these hypotheses, we compiled records of wounds suffered by chimpanzees in four communities at three long-term study sites (Gombe, Tanzania; Kibale, Uganda; Fongoli, Senegal), including both nonlethal (N = 1,268 wounds; N = 891 male wounds; N = 377 female wounds) and lethal attacks (N = 258 wounds), to determine whether genital wounding occurred more frequently than expected by chance. In nonfatal cases, wounds occurred in the genital region more often than expected for females (Kasekela: N = 9/80 wounds, Mitumba: N = 8/61 wounds, Fongoli: N = 11/84 wounds, Kanyawara: N = 31/152 wounds), but only in Kasekela did males suffer genital wounds more often than expected by chance (Kasekela: N = 3/80 wounds, Mitumba: N = 2/48 wounds, Fongoli: N = 6/413 wounds, Kanyawara: N = 4/350 wounds). In contrast, killings of males involved genital wounds more often than expected (N = 12/258 wounds). Increased genital wounding may occur when genitals are more accessible, such as when females flee from male aggression, exposing their hindquarters, or when victims are immobilized during fatal attacks.