Eusociality in a mammal: cooperative breeding in naked mole-rat colonies.

Laboratory observations on a field-collected colony of 40 Heterocephalus have shown that only a single female breeds. The remaining individuals constitute two or three castes, each containing both sexes and distinguishable by size differences and the tasks they perform. These features, together with long life-spans, overlap of generations, cooperative brood care, and possible age polyethism provide parallels with the eusocial insects.