Relatedness modulates reproductive competition among queens in ant societies with multiple queens

Reproductive sharing in animal groups with multiple breeders, insects and vertebrates alike, contains elements of both conflict and cooperation, and depends on both relatedness between co-breeders, as well as their internal and external conditions. We studied how queens of the ant Formica fusca adjust their reproductive efforts in response to experimental manipulations of the kin competition regime in their nest, as well as their own reproductive status. Queens respond to the presence of competitors by increasing their egg laying efforts, but only if the competitors are highly fecund and distantly related. Furthermore, queens only engage in cannibalism of eggs when the risk of erroneously destroying own offspring is absent. We demonstrate that queens of Formica fusca fine-tune their behaviours in response to kinship and fecundity of others as well as their own physiological state in a manner that is unusually precise for any cooperative breeder.