Aggression and motivation to disperse in eusocial naked mole-rats, Heterocephalus glaber

Abstract

Naked mole-rats are eusocial mammals that live in hierarchies consisting of one breeding female, one to three male consorts and their reproductively suppressed offspring. A ‘disperser morph’ subcaste has been suggested with a subset of nonbreeders exhibiting motivation to leave their natal colony and mate with unfamiliar conspecifics. To test the hypotheses that intrinsic colony variables (e.g. population density, sex ratio, queen temperament) influence the dispersal phenotype, and that males and females differ in responsiveness to these variables, we evaluated dispersal behaviour in 17 laboratory colonies. Queen aggression was associated with the number of female, but not male, dispersers, although dispersers were not themselves targets of queen aggression. Female dispersers were more aggressive than their nondispersing sisters, although still less aggressive than queens overall. Following outpairing with an unfamiliar opposite-sex animal, dispersers and nondispersers produced litters at similar rates, demonstrating that motivation to leave the colony, and not anticipatory reproductive maturation, is the key to successful dispersal. Collectively, these data suggest that aggressive naked mole-rat queens motivate dispersal in their daughters and that female dispersers show traits consistent with successful queens (e.g. aggression).