Infanticide and cannibalism in wild common marmosets.

Infanticide has been observed in many different species [1], including common marmosets [2-4], due to sexual selection, reproductive strategies or resource competition [3, 5, 6], which may ultimately lead to exploitation (cannibalism) [1, 7]. Wild callithrichids have a very flexible mating system, including monogamy, polygynandry, polyandry and polygyny [4, 8, 9], with Monteiro da Cruz [10] finding all these patterns within the same population. This results from the high degree of deforestation of their habitat [4], but non-monogamous groups cannot ensure successful rearing of infants, since helpers are crucial and should be present in high numbers [11]. In this study, we show for the first time that cannibalism can follow infanticide, and we hypothesise that it is a result of both competition for scarce resources and the need for animal protein, exacerbated by forest degradation.