Naked Mole Rat
The Naked Mole Rat (Heterocephalus glaber), also known as the Sand Puppy, or desert mole rat, is a burrowing rodent native to parts of East Africa. It has a highly unusual set of physical traits that enable it to thrive in a harsh, underground environment. This includes a lack of pain sensation in its skin, and a nearly cold-blooded metabolism.
Typical individuals are 3.15 to 3.94 inches(8 to 10 cm) long and weigh 1.06 to 1.23 ounces (30 to 35 g). Queens are larger and may weigh over 1.76 oz (50 g), the largest reaching 2.82 (80 g). They are well adapted for their underground existence. Their eyes are just narrow slits, and consequently their eyesight is poor. They are highly adapted to moving underground, and can move backwards as fast as they move forwards. Their large, protruding teeth are used to dig. Their lips are sealed just behind their teeth while digging to avoid filling their mouth with soil. Their legs are thin and short. They have little hair (hence the common name) and wrinkled pink or yellowish skin.
The naked mole rat is well adapted for the limited availability of oxygen within the tunnels that are its habitat. Its lungs are very small and its blood has a very strong affinity for oxygen. This increases the efficiency of oxygen uptake. It has a very low respiration and metabolic rate for an animal of its size, thus using oxygen minimally. In long periods of hunger, its metabolic rate can reduce up to 25 percent.
The naked mole rat is unique among mammals as it is virtually cold-blooded. It cannot regulate its body temperature at all and requires an environment with a specific constant temperature in order to survive.
Distribution and habitat
The naked mole rat is native to the drier parts of the tropical grasslands of East Africa, predominately South Ethiopia, Kenya, and Somalia
Clusters of 20 to 300 animals live together in complex systems of burrows in arid African deserts. The tunnel systems built by naked mole rats can stretch up to two or three miles in cumulative length.
Social structure and reproduction
Naked mole rats have a complex social structure in which only one female (the queen) and one to three males reproduce, the rest of the members of the colony function as workers. The workers are divided along a continuum of different worker-caste behaviors instead of discrete groups. Some function primarily as tunnelers, expanding the large network of tunnels within the burrow system. Others are primarily used as soldiers, designed to protect the group from outside predators.
The relationships between the queen and the breeding males may last for many years. A behavior called reproductive suppression is believed to be the reason why the other females do not reproduce. This means the sterility in the working females is only temporary, and not genetic. Queens live from 13 to 18 years, and are extremely hostile to other females behaving like queens. When the queen dies, another female takes her place, sometimes after a violent struggle with her competitors.
The naked mole rats feed primarily on very large tubers (weighing as much as 1000 rats) that they find deep underground. They also eat their own feces. A single tuber can provide a colony with a long-term source of food. This can last for months, or even years.