Which mammal lives in colonies organized like a beehive, with a single breeding 'queen', a few breeding males, and non-breeding worker and soldier castes?
- The prairie dog
- The capybara
- The naked mole-rat
- The Alpine marmot
Why C? And why not the others?
Correct answer: C. The naked mole-rat
The naked mole-rat is one of only two mammal species known to be truly eusocial: a single queen suppresses the fertility of other females hormonally, a small number of males breed with her, and the rest of the colony forms non-breeding worker and soldier castes that dig tunnels, gather food, and defend the group, much like a termite or bee colony. Naked mole-rats are also famous for extreme longevity for their size and unusual cancer resistance. Prairie dogs form elaborate underground 'towns' with sophisticated alarm calls, but every female can breed and there is no worker or soldier caste, so the colony is social rather than eusocial. Capybaras live in cohesive family groups but follow an ordinary mammalian breeding pattern with no reproductive caste system at all. Alpine marmots hibernate as extended families and dominant pairs do suppress some subordinates' breeding, but the colony never develops the physically distinct worker and soldier castes that define true eusociality.
Source: Smithsonian's National Zoo: naked mole-rat eusociality; Jarvis, 'Eusociality in a mammal: cooperative breeding in naked mole-rat colonies,' Science 212, 1981.