Social conflict in ant larvae: egg cannibalism occurs mainly in males and larvae prefer alien eggs

Abstract

In social organisms, cooperation is widespread. However, social groups also provide excellent opportunities for individuals to exploit the cooperative efforts of others, thus creating conflict. Social conflict is particularly common in ant societies but although much is known about conflicts between adult individuals, the selfish interests of developing offspring have been largely neglected. One taxonomically widespread way for offspring to engage in competition is through egg cannibalism. Here, we show that larvae of the ant Formica aquilonia compete by eating eggs, which increases their survival. Cannibalism behavior differs strongly between sexes, and males cannibalize 3 times as often as females. This points to sex-dependent benefits from cannibalism, for males possibly through removal of future competitors for mating opportunities. Larvae also preferentially eat eggs of distinct origin and odor profile, suggesting that they can detect and react to chemical cues. Thus, similar to adult ants, larvae possess the power to adjust their behavior to available information. We conclude that exploring the behavior of developing individuals can give new insight into social conflict in ants and social animals in general.