Lethal combats in the forest among wild western gorillas

Lethal inter-group encounters occur in many species because of sexual selection. While documented in mountain gorillas, they are absent in western gorillas as instead it is predicted by their higher feeding (frugivory) and mate competition (single- vs. multi-male groups). We investigate whether the injuries on three dead silverbacks and one adult female from four groups of western gorillas in Central African Republic, resulted from interactions with gorillas or leopards. We identified two distinct injury patterns caused by gorillas (isolated lacerations, round wounds) and leopards (punctures clustered on head/neck) by analysing injuries caused by mountain gorillas and leopards to gorillas and non-gorilla species, respectively. The western gorilla injury pattern is similar to that of mountain gorillas suggesting that lethal encounters occur, albeit infrequently, as predicted by sexual selection in one-male society. While sexual dimorphism and polygynous sociality favoured the evolution of violent encounters, multiple males in groups may influence their frequency.