Naked mole-rats have wrinkly pink or grayish-pink skin, which is somewhat translucent on the underside and light purplish-brown on their backs and tails. This countershading appears to be lost with advanced age. They have short, broad heads with powerful jaw muscles and very large incisors, which are used to dig tunnels.
Naked mole-rats are usually 3 inches (7.5 centimeters) long and usually weigh 1 to 1.5 ounces (28 to 42 grams), however, soldiers can weigh up to 2 ounces (57 grams), and the queen, who is the largest member of the colony, can weigh up to 2.5 ounces (71 grams).
Naked mole-rats are found in eastern Africa, specifically in Ethiopia, Kenya and Somalia. They live exclusively in underground burrows and tunnels in grassy semi-arid regions.
They have no external ears and tiny eyes, which make them virtually blind. Their sense of smell is important, and they are also very sensitive to vibrations in the ground and the movement of air currents.
These burrowing rodents eat the underground parts of plants, particularly the succulent tubers formed by many of the plant species that grow in arid areas. They obtain all the water they need through their food; they do not drink.
When a group of mole-rats finds a large tuber (sometimes more than a foot in diameter), they generally bore through it, eating mainly the interior flesh while leaving the thin epidermis intact. This behavior may allow the plant to remain healthy for some time, indeed even to continue growing, thereby providing a long-term food resource for the colony.
Their diet is high in cellulose, which is difficult to digest. Naked mole-rats have high densities of gut fauna that aid in digestion. They also regularly practice coprophagy, the reingestion of feces, which allows them to maximize their uptake of nutrients from their food.
At the Smithsonian's National Zoo, they are fed apples, carrots, corn, green beans, kale and sweet potatoes as well as leafeater biscuits.
Only one female in a colony of naked mole-rats produces offspring; this female is called the queen. She mates with only a few of the colony's males and these relationships can remain stable for many years. All of the other individuals in the colony aid in the queen's reproduction by caring for the pups, foraging for and providing food, and maintaining and defending the burrow system. These "workers" are physiologically capable of reproduction, but do not do so as long as they remain in the colony (which in most cases is their entire lives).
Gestation lasts about 70 days. A queen can produce a new litter every 80 days and can have up to five litters per year. Pups generally weigh less than 0.07 ounces (2 grams) at birth. The number of pups per litter is quite variable. The average is about 12, with a maximum of about 30, the largest known litter size of any mammal. The queen nurses the pups for about a month, although they may begin eating solid food at as early as two weeks of age. Pups also eat feces that are provided for them on demand by the workers. This not only provides nutrition, it also inoculates their digestive system with beneficial gut fauna.
Pups begin performing work behaviors (digging, sweeping, carrying, etc.) at the age of three to four weeks. Maturation rate is variable, but in general juveniles are physiologically capable of reproduction by the age of one year.
Naked mole-rats may have a life span of 10 to 30 years. Maximum longevity in this species is as yet unknown; animals have been in human care for as long as 30 years. This life span is unprecedented among small rodents.
There are no immediate, major threats to naked mole-rats. They are often seen as pests, especially for sweet potato farmers because they can destroy much of a crop yield by eating the roots of plants. Due to habitat fragmentation, naked mole rats may face the threat of an unhealthy genetic population in the future.
Continued monitoring is necessary to better understand these unique animals. Minimal development and human interference exists in their present range, but if agriculture continues to expand they could be viewed as pests, as they will readily consume roots and tubers.
Distribution of colonies is patchy, although naked mole rats do reside in multiple protected areas. They are also well represented in zoos, with well-established and maintained colonies. With a variety of unique characteristics, the species is significant to research on a number of different topics.
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