Ant queens cannibalise infected brood to contain disease spread and recycle nutrients

Filial cannibalism, where parents eat their own offspring, is a taxonomically widespread behaviour with a multitude of potential adaptive explanations¹. Of these, the impact of pathogens on the expression of filial cannibalism is, in particular, poorly understood. Cannibalising young with low survival probability may enable parents to reinvest valuable resources into future reproduction¹. However, cannibalising offspring that harbour pathogens may be potentially harmful to parents, and such risk may therefore select against this behaviour. Although disease-induced cannibalism of eggs has been reported in fish², the benefits of consuming infected brood to contain infections - as an explanation for the evolution of filial cannibalism - remain largely unexplored. Here, we demonstrate that solitarily founding ant queens cannibalise sick larvae in their nests before they become contagious, showing that filial cannibalism both contains an otherwise lethal infection without any long-term consequences on queen survival and also enables the reinvestment of recouped energy into additional egg production.