African Mole-Rats: Bathyergidae

Physical characteristics: Naked mole-rats, sometimes called sand puppies, are the smallest of the mole-rats. Even though they are called both moles and rats, they are much more closely related to porcupines, chinchillas, and guinea pigs. They are nearly hairless except for scattered sensory hairs. They lack the fur typically found on rodents have underdeveloped eyes and pinkish brown to pinkish gray wrinkled skin, long buck teeth, and long tails. Adults have an average length of 3 inches (7.6 centimeters), and an average weight of about 1.2 ounces (34 grams). Males and females look alike but size varies with social status; and dominant individuals can weigh up to 2.8 ounces (80 grams).

Naked mole-rats live almost their entire lives in the total darkness of underground burrows, living in the same home range for many years. (© Gregory G. Dimijian, M.D./Photo Researchers, Inc. Reproduced by permission.)

Geographic range: They are widely found in the regions of the Horn of Africa; that is, the east-central Africa area that includes Ethiopia, Somalia, and Kenya.

Habitat: Naked mole-rats inhabit dry regions with an average annual rainfall of under 15.6 inches (40 centimeters). They like fine sandy soils that become very hard in dry seasons.

Diet: Their diet consists of geophytes that are found through the coordinated foraging, searching for food, of colony members. They almost constantly dig tunnels in search of irregular food supplies and to escape snakes, their primary predator. The animals also eat feces, solid bodily waste; in fact, the breeding female and the weaning pups often beg for feces from colony members.

Behavior and reproduction: Naked mole-rats are highly social animals, living in complex underground colonies, which is unique among mammals, and much more common among insects, with 20 to 300 animals, but with an average of 75. They live almost their entire lives in the total darkness of underground burrows, living in the same home range for many years. The rodents have very underdeveloped eyes so, instead, use highly accurate sensitivities to vibrations in the ground. They show a very highly developed division of labor that is centered on reproduction. One breeding female mates with several males, often one to three; all such animals are called the breeders. All other members are non-breeding worker and soldier animals that are offspring of the breeders and do all the jobs necessary within their territory in order to ensure the success of the group.

The breeding female stops non-breeding members from breeding with aggressive behaviors. Most non-breeders never leave the colony or breed. Odors separate friends from enemies, which is achieved by all members from rolling about in the burrow's toilet chamber, and coating their bodies with the familiar scent of the colony's feces and urine. Naked mole-rats will fiercely attack unfamiliar intruders, such as when another colony breaks into another colony's burrow system. Some breeding occurs outside the colony from animals that are highly sexed and attracted to animals from other colonies.

The breeding female has a distinctive elongated body and up to seven pairs of nipples. Her breeding occurs throughout the year. The gestation period is sixty-six to seventy-four days. The average litter size is one to twenty-eight, but the average size is twelve. Up to four litters are born each year. They live long lives, and females are able to reproduce into old age.

Naked mole-rats and people: There is no known significance between people and naked mole-rats.

Conservation status: Naked mole-rats are not threatened. ∎