Mating status and kin recognition influence the strength of cannibalism

Adults that cannibalize juvenile conspecifics gain substantial energy and nutrients that are potentially limited in their normal diet, but they may also face the risk of filial cannibalism: the consumption of an individualʹs own offspring. However, the potential costs and benefits of cannibalism change with the reproductive status of an individual during its lifetime. Once adults become reproductively active, they suddenly face the potential loss of inclusive fitness associated with filial cannibalism, but they also have higher energy demands that could easily be met with cannibalism. Thus, selection should favour any behaviour that reduces the risk of filial cannibalism while maximizing the nutritional and other benefits of cannibalism. Here we take an experimental approach to examine the relative importance of kin discrimination, reproductive status and sex differences in influencing cannibalistic behaviour (including filial cannibalism) of adults using confused flour beetles, Tribolium confusum, as a model system. Using a series of complementary experiments, we show that the cannibalistic behaviour of T. confusum is driven by a combination of two factors that both reduce the risk of filial cannibalism. First, reproductive females preferred to cannibalize unrelated eggs over related eggs, indicating clear kin discrimination. In addition, females also showed a dramatic reduction in the general propensity for cannibalism after becoming reproductively active. Interestingly, the onset of reproduction also reduced cannibalism rates in males, indicating that this change in cannibalistic behaviour is consistent across sexes. Mating status had a greater influence on cannibalism rates than did sex. Together, kin discrimination and mating-status-dependent shifts in cannibalism rates reduced the risk of filial cannibalism by up to six-fold. In general, our findings suggest that evolution can alter the cannibalistic behaviour of individuals in multiple ways to reduce the risk of filial cannibalism while still maximizing the benefits of cannibalism.