First mammal joins the eusocial club

For years, scientists have observed that just one female naked mole rat in a colony of about 80 animals does all of the breeding. Several generations of sterile offspring take care of the queen and her newest pups. This sort of community is typical of insects like bees, termites, ants, and wasps—not mammals—but some scientists have resisted grouping the naked mole rat with the so-called eusocial insects.

Although naked mole rats appeared to live eusocially, they hadn't met a crucial criterion: permanent, physical traits that distinguish certain castes of a colony. For instance, queen ants have wings, but worker ants don't.