Naked mole-rats are small rodents that live in large underground colonies in dry areas of East Africa. One of the most unusual of all mammals, they look a little like small, wrinkled, pink sausages, with legs, a tail and very big front teeth. The name naked mole-rat is misleading. Although they may look completely naked at first glance, they do have whiskers on the head, as well as hairs in other spots, including the tail and between the toes. And although they burrow like a mole and look like a hairless rat, they aren't really either one. They are rodents, like rats and unlike moles, but they are more closely related to the porcupines of North and South America and some other American rodent groups than they are to real rats.

As if their appearance were not enough, the naked mole rat has many other claims in the contest for "Earth's weirdest mammal." Keep reading to find out more.
 

Naked mole-rats have remarkably long life-spans for their size. They can live to more than 27 years of age in a zoo or laboratory and to at least 17 years in the wild. Scientists are studying this species to try to understand the physiological basis for their long lives, which are much longer than those of other small rodents. This research could tell us more about the aging process in general.

Of course, most individual mole-rats don't reach the maximum age. And it appears that the role or "job" an individual has in the colony affects how long he or she will live. In zoos or laboratories, both workers and reproductive individuals have long life-spans. But in the wild, it appears that only the breeding animals are long-lived. Workers in the wild typically live only two or three years.  

 
A rodent with a "job"? We'll get to that next.
 

Naked mole-rats live in large underground colonies. The largest colonies may contain 295 animals or more, but a colony might more typically hold 70-80 members.

In terms of social behavior, naked mole-rats are among the most fascinating mammals in the entire world. Within each mole-rat colony, there is social structure that is similar to that seen in some insects, like ants and honeybees, with different categories of animals that have different "jobs" in the colony.  There is usually just one breeding female, the queen, and only 1-3 males that might breed with her. Most of the other adults in the colony look for food, help to maintain the burrows, or defend the colony against attackers.  Most of these "workers" will never reproduce themselves and spend their entire lives helping to raise or protect the offspring of the queen and her mates.

 
There is also some differentiation within the worker group. "Housekeepers" find and transport food, dig new tunnels and repair existing tunnels. "Soldiers", who tend to be the largest of the workers, protect the colony against predators and against other mole-rats, if the group encounters a neighboring colony while tunneling.

A mole-rat colony creates a huge underground network of burrows and chambers, which can include more than two miles of tunnels and can cover an area the size of 20 football fields. Mole-rat workers build these incredible networks using only their teeth to dig! Why go to all the effort of these extensive tunnel systems? Naked mole-rats live on tubers and other underground roots and worker tunnel, apparently in a random fashion, to find the food for the colony. If the workers didn't keep digging new tunnels to find food, the entire colony would starve.

Within the tunnel system, there are also "rooms" or chambers with particular functions. The nesting chamber is where the entire colony piles together to rest or sleep, and where the babies are born. The colony may move to a new nest chamber to be closer to a new source of food found by the workers. There is also a toilet chamber, a dead-end room where all the animals urinate and defecate, keeping the waste in a small area. When the toilet chamber fills up, the mole-rats dig a new one. 

Most of the time, the tunnel system of a naked mole-rat colony is sealed, with no hole to the surface. So oxygen levels may be low and carbon dioxide levels high. How do the animals keep from suffocating? Naked mole-rats have a metabolic rate that is less than half that of other rodents, so they need less oxygen to maintain basic functions. And they have a different form of hemoglobin from other animals, which is more efficient at capturing oxygen to carry through the bloodstream, and can therefore keep the body fully supplied even when the level of oxygen in the air is low. 

In most naked mole-rat colonies, only the dominant female (the "queen") breeds.  After a gestation period of 70-80 days, she will give birth to a litter of 5-15 pups.  Litters of over 25 have been recorded.  The queen typically breeds year-round, and becomes pregnant again soon after the birth of a litter.  One female in a laboratory colony produced over 900 pups in a 12-year period. 

If the queen dies, several females may fight to become the next queen. The new queen will grow longer and thus become bigger than the other members of the colony.  It is very unusual for a mammal to grow taller or longer after reaching full adulthood. Imagine a human having a growth spurt at 25! 

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