First eusocial mammal

The first species of mammal in which a system of reproduction and labour division comparable to that of eusocial insects (ants, termites, certain bees and wasps) was discovered was the naked mole-rat Heterocephalus glaber, a burrowing species native to the dry savannah of Kenya, Somalia and Ethiopia, and the only member of an entire taxonomic family, Heterocephalidae. Its highly-specialized eusocial colony organization, consisting of a single breeding queen and various sterile non-breeding worker castes between which labour is divided, was first formally documented in the scientific literature in May 1981, following laboratory observations on a field-collected colony of 40 specimens.

Although not widely known outside mammalogical circles, several other species of mole-rat, belonging to the taxonomic family Bathyergidae (in which the naked mole-rat was also originally classed before being split off more recently by researchers into its own family), also show a degree of eusocial organization within their colonies, albeit to a much less pronounced degree than that of the naked mole-rat. The most prominent of these is the Damaraland mole-rat Cryptomys (=Fukomys) damarensis of southern Africa. Additionally, some species of vole, such as the prairie vole Microtus ochrogaster of central North America, may fulfil certain criteria for mammalian eusociality.