NAked mole rat

Physical features

• Their skin is pink and somewhat translucent on the underside and light purplish brown on their backs and tails.

• Naked mole rats are not completely naked. They have sensory whiskers on their faces and tails. They also have hair between their toes which allows their feet to function as brooms when sweeping away soil.

• They are more closely related to porcupines, chinchillas and guinea pigs than rats or moles.

• Naked mole rats lack sweat glands and an insulating layer of fat directly under their skin. The low metabolism helps prevent over heating. Mole rats will huddle and sleep together in warming groups to gain heat.

• When a female becomes a queen she actually grows longer, even though she is already an adult, by increasing the distance between the vertebrae in her spine.

• They are not sexually dimorphic; males and females look alike, with the queen’s size being the exception to the rule.

Diet: Herbivore

• Wild – roots and tubers that are 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; They are coprophagic, meaning they will eat their own feces to maximize digestion.

• Zoo – sweet potatoes, baby cereal, various fruits, romaine lettuce

Reproduction

• Only the queen produces offspring. She mates with one to three males in the colony. These relationships can remain stable for many years.

• The queen is the only one reproducing so inbreeding is common.

• All of the other individuals in the colony aid in the queen's reproduction by caring for the pups, foraging and providing food, and maintaining and defending the burrow system.

• The duration of gestation is approximately 70 days. A queen can produce a new litter every 80 days, and can have up to 5 litters per year.

• Most mammals exhibit the ½ rule which is the average number of offspring equals ½ of the number of mammary glands. This is not the case for naked mole rats. The queen has 11 glands and average 12+ pups.

• If the colony grows too large the group begins to practice infanticide.

Interpretive Information

• Colonies usually range around 70 in number but colonies of up to 295 have been observed.

• They are one of two truly social (eusocial) mammals. This behavior is typical to insects, where there is a queen and then supporting castes. Termites and naked mole rats have exactly the same social structure.

• Naked mole rats are completely fossorial (living underground) in complex burrow systems. The tunnels are about 4 cm in diameter. Some tunnels run just under the surface of the ground, while others can be up to 2 m deep. There is a great deal of branching and interconnection of tunnels, with a colony's total tunnel length potentially adding up to 4 km.

• Tunnels connect nest chambers, toilet areas, and food sources. Each of these chambers acts as a different “room in their house,” and serves a specific duty.

• Burrowing is the only way these animals find food, since they do not travel above ground.

• Workers dig through the hard-packed soil with their powerful ever-growing incisors. 25% of their muscle mass is dedicated to the jaw. Humans dedicate 1% to their jaws.

• A molerat's lips actually close behind its incisors, so it can dig without getting dirt in its mouth.

• 1/3 of a naked mole rat’s brain is used to process information from around its teeth.

• They work assembly-line style, with the front animals actually breaking through the dirt while a string of workers sweeps the soil through the tunnel system to an opening to the surface, where another worker kicks the dirt up onto the ground above its head, forming a mole hill.

• They are highly sensitive to air currents and vibrations. An important part of the exhibit design is to limit air flow, sound, and vibrations.

• Naked mole rats live in such a harsh environment that their skin does not feel pain when exposed to normally noxious substances (such as acid).

• Zoo Atlanta is currently involved in research projects that utilize the carcasses of pups that have died in our colony to study molecular ecology of the naked mole rat.

Updated January 2008