Twenty years ago today, the Smithsonian’s National Zoo welcomed naked mole-rats (Heterocephalus glaber) into its collection. These rodents, which are more closely related to porcupines and guinea pigs than to their namesake, are one of only a handful of mammals that exhibit eusocial behavior. Like insects such as termites and bees, naked mole-rats follow a hierarchical social structure that consists of one breeding female called the queen, up to three breeding males and many non-breeding workers and soldiers. In the wild, a single colony may contain as few as 20 individuals or as many as 300 individuals.

Eleven naked mole-rats are currently on exhibit at the Zoo’s Small Mammal House, though two other colonies, each comprised of nine individuals, live off-exhibit. Nearly 300 naked mole-rat pups have been born here and survived to adulthood since 1991. However, no pups have survived in the last 10 years. For unknown reasons, it is common for captive colonies to self-regulate their population. In the wild and in human care, these animals can live upwards of 30 years old.

Naked mole-rats are native to the arid-desert and semi-grassy regions of Ethiopia, Kenya and Somalia in Eastern Africa and spend most of their lives navigating through dark underground tunnels. Because they have poor eyesight, they rely on smell, touch and hearing to get around. Measuring only three inches long, these rodents sport very little hair and have bare, wrinkly skin which varies in color from pink to grayish-pink. In addition to hairy feet, they also have hairy mouths that prevent them from swallowing dirt while they dig with their large incisor teeth.

Visitors to the Zoo’s website can watch these fascinating animals on a naked mole-rat web cam.