Class: Mammalia (Mammals)
Body length: 3 to 4 inches (8 to 10 centimeters)
Tail length: up to 3 inches (8 centimeters)
Weight: 1 to 1.8 ounces (30 to 50 grams)
Life span: nearly 30 years in zoos; unknown in the wild
Gestation: 70 days
Number of young at birth: 12 to 27
Weight at birth: 0.07 ounces (2 grams)
Age of maturity:
Conservation status: lower risk
About 25 percent of a naked mole-rat's muscle mass is in its jaws!
• The dominant female, or queen, has 12 nipples to feed up to 25 pups!
• Naked mole-rats can run both forward and backward though the maze of tunnels they dig.
• The mole-rat family name, Bathyergidae, comes from the Greek bathos, meaning depth, and ergon, meaning work or worker.
• Naked mole-rats have been known to chew through concrete!
• Many people in Africa call these animals "sand puppies."
Mammals: Naked Mole-rat
Not a mole, not a rat
Yes, these odd little creatures with pink, wrinkly skin dig and live in underground burrows the way moles do. Yes, they have skinny, rat-like tails. Yet naked mole-rats are more closely related to porcupines, chinchillas, and guinea pigs than they are to moles or rats and are the only species of mole-rat that has practically no hair.
Why are they "naked"? Naked mole-rats live underground in the desert regions of East Africa, a pretty warm place during the day. If it does get cold at night, the little mammals just huddle together in a mole-rat pile and use each other's body heat to keep warm. And since they spend their lives underground, they don't need hair for sun protection. It's hard to see, but naked mole-rats do have about 100 fine hairs on their bodies that act like whiskers to help them feel what's around them. Hairs between their toes help sweep soil behind them while tunneling.
Most mole-rat species live by themselves. But the naked mole-rat and the Damaraland mole-rat Cryptomys damarensis are the only two mammal species that are eusocial (yew SO shul). This means they live in colonies that may have several generations living together and just a few individuals that produce all the offspring for the colony, much the way bees and ants live. Scientists believe the naked mole-rats' eusocial behavior is due to the challenges of living underground in the desert, where there is little food or water.
Life down below
A naked mole-rat colony may have from 20 to 300 individuals living in an underground area that can be as large as 6 football fields! The area is filled with a tunnel system that stays at a warm temperature of 86 degrees Fahrenheit (30 degrees Celsius), even though the outside temperature can get much colder or much warmer. To keep the colony healthy and safe, there are chambers, or rooms, at different points along the tunnel system. Each chamber has a purpose, just like the rooms in your home. There is the nesting chamber, or nursery, where the queen (dominant female) stays with the pups (babies), and feeding chambers, used for collecting and storing food—a mole-rat pantry! There is even a toilet chamber, where the members go to the bathroom (sorry, no shower).
Is it day or night?
Most people think naked mole-rats are blind. Their tiny eyes are not much use underground, but they can still see a little bit. However, mole-rats rely on their senses of hearing, smell, and touch more than their sight. Researchers have studied them in light and dark environments and find their behavior doesn't change.
Everyone has a job
The colony has a specific job for each member and is led by the queen. Only a small group of males is allowed to mate with the queen. The other naked mole-rats in the colony serve as soldiers or workers. If a snake or other predator comes into a tunnel, the mole-rats let out an alarm call to alert the soldiers. Like a little army unit, the soldiers run off to defend the colony with their large, sharp teeth. Several of the soldiers may pile on top of each other to block the way, and all the predator sees is many sets of gnashing teeth! The mole-rats assigned as workers scout for food, dig the tunnels, and care for the queen's pups.
"Because I’m bigger and I said so"
The queen of the colony is larger and longer than all the other mole-rats. Her job is to breed and have pups and to keep her position as the dominant mole-rat in the colony. But the queen is not born into her position: she must earn it. Females will fight, even to the death, for the right to be queen. Once a queen is established, she will actually stretch the space between the vertebrae in her backbone to become longer and get ready to have pups. Her position as queen is never secure and she must continue to fight off other females if she wants to stay in charge. The queen often inspects the tunnels and chambers and tries to keep control of her colony by biting and pushing the other mole-rats to remind them she is the boss.
Queen and mother
The queen's workers dig all day to bring her food so she can devote her time to reproduction and the care of her pups. It's a good thing she has help, because a naked mole-rat queen can have up to 27 pups at a time. That's a lot of little ones to care for, and she can give birth four or five times a year—whew! After each helpless pup is born, it is cleaned and carried to the nursery by a worker. The queen will come into the nursery to nurse her pups. Within a few weeks, the pups start to explore the tunnels, and in a few months they take their place as part of the workforce. By one year of age they are fully grown.
Now be nice and share
A naked mole-rat colony works together for the good of the group, and that includes sharing food. Scientists who study naked mole-rat behavior have even seen pups take turns nursing. If a food scout finds a tasty root or tuber, he or she will carve off a piece with those sharp teeth and dash back to the group while chirping and waving the morsel overhead! The other workers will follow the scout's scent back to the new food source and bring it back, piece by piece, to the food chamber.
Long in the tooth
Eating tough roots and tubers requires some pretty strong and sharp teeth. A naked mole-rat's front teeth also help them tunnel through dirt while looking for these food items. Like all rodents, these teeth continue to grow, but by gnawing on hard things, they keep their teeth from getting too long! The animal can move its front teeth independently, spreading them apart and moving them together, like a pair of chopsticks. Naked mole-rats at the San Diego Zoo are fed yams, carrots, corn, broccoli, and fruit. Their favorite food item is a banana.
They eat what?
Yucky, but true: naked mole-rats eat their own poop. But they have a very good reason for doing this. Naked mole-rats eat roots and tubers, which are very hard to digest. Their intestines are full of microscopic organisms to help with digestion. But in order to absorb more of the nutrients from their food, they will eat the poop. It's like getting two meals for the price of one. And not only do they eat their feces, they also roll in it! Because naked mole-rats live in the dark, they have nearly lost the use of their eyes. In order to identify members of the colony versus an intruding colony, they all roll around in the toilet chamber. This way everyone smells the same!