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Heterocephalus glaber
Physical Characteristics
- Despite their name, naked mole rats are more closely related to guinea pigs and chinchillas than they are to either rats or moles. Naked mole rats are unique among mammals in that they are ectotherms, meaning that they are almost cold-blooded and therefore cannot regulate their body temperatures. Thus, they depend on the environment maintaining a constant temperature of 82 to 87° F, with 30 to 80 percent humidity.
- Naked mole rats lack fur, but they are not entirely without hair. Long whiskers and sensory hairs on the tails facilitate movement both forward and backward, and hairs between the toes act as sweeping mechanisms.
- Uniquely evolved long, sharp front incisors are capable of moving independently, enabling the animals to tunnel effectively through dirt. Naked mole rats’ teeth continue to grow throughout their lives – only constant wear keeps them from growing to unnatural lengths.
- Naked mole rats are not blind, but their vision is poor. The animals capitalize instead on their more highly developed senses – hearing, touch and smell.
- Naked mole rats have adapted to the limited availability of oxygen underground; they have very small lungs, and their blood has mechanisms for increasing the efficiency of oxygen uptake.
- Because they live in a harsh underground environment, naked mole rats lack pain transmitters or pain sensations in their skin.
Habitat and Diet
- Naked mole rats are subterranean or fossorial (living completely underground) and are found in drier tropic grassland areas of southern Ethiopia, Kenya and Somalia.
- Wild diet includes roots and tubers. Naked mole rats don’t drink water; they acquire all necessary moisture from their food. Superbly evolved for life underground, these subterranean mammals also occasionally eat their own feces – a practice that is difficult for humans to conceive but that helps to maximize nutrient absorption from digested food.
Behavior and Communication
- Naked mole rats and their cousins the Damaraland mole rats are the only two mammals known to exhibit eusocial behavior. Similarly to that of bees, ants or wasps, naked mole rat life revolves around the service of a queen.
- Colonies may number up to up to 300 individuals and cover territories as large as six football fields. Naked mole rats designate individual underground chambers for specific purposes: nursery, bedroom, food pantry and restroom.
- Social structure is based on a highly organized caste system, with each animal performing a particular task:
The queen
- The queen is the central focus of the colony, serving as leader, taskmaster and sole mother. When she is not busy with her primary duty – reproduction – she patrols the tunnels to ensure that each of her subjects is doing his or her job. Those found not performing their duties are nudged or bitten into activity.
- The queen is not born to her role; rival females fight for the right to assume leadership of the colony. The winner then undergoes one of the animal kingdom’s most unusual transformations. The new queen’s body expands with additional vertebrae, making her visibly longer and larger than other colony members. (Her added size helps her to accommodate her numerous pregnancies, and her length enables her to pass through tunnels without getting stuck.)
Breeders
- A small elect of one to three males serve the sole function of breeding with the queen; only these individuals are permitted to do so.
Soldiers
- Soldiers defend the colony from predators. Naked mole rats occasionally fall prey to jackals, snakes and even large spiders searching for underground snacks. (Soldiers often inadvertently serve the colony by becoming meals themselves.)
Workers
- Housekeepers transport materials and keep tunnels free of debris.
- Volcanoers dig new tunnels and chambers and push excess dirt out of burrows.
- Nest-builders gather materials and prepare the queen’s birthing chamber for new litters of pups.
- Body warmers absorb the sun’s heat near the surface and share the warmth with the rest of the colony.
- Workers also scout for edible vegetation, deliver food to the queen, and contribute to nursery care.
Status in the wild
Naked mole rats are not currently listed as endangered. They are, however, considered crop pests in some areas.
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Reproduction
- Only the queen reproduces. She gives birth to all of the colony’s offspring – up to 27 babies at a time and as many as 500 in her lifetime.
- Litters are born at 80 to 90-day intervals.
- The queen nurses her pups in a designated nursery chamber. Naked mole rat pups are mature by the age of 1 and begin assuming tasks within the colony when they are only a few months old.
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Lifespan
While wild lifespan is not known, naked mole rat queens tend to have lifespans of 13 to 18 years in captive environments, while other colony members have been known to live 20 to 30 years. |
