Awesome Animal - Naked Mole Rat

Okay, I've been waiting to feature this animal for a long time. The naked mole rat does not make an appearance in any of my novels (at least not yet), but I am simply fascinated by this creature.

What is your concept of beauty? I don't mean physical beauty of people, which is greatly over-emphasized in pop culture. I'm talking about beauty in nature. Some people might think beauty is tall, snow-covered mountains. Others might think it's a wide open, undisturbed grassland, or an ancient forest. Or perhaps an animal, like a zebra or a bird of paradise. Well, beauty doesn't have to be physical (I'm not sure anyone would say these creatures are physically beautiful). But beauty can also be in the astounding adaptations of an animal or plant. Or in a bacterium, protozoan, or fungus, for that matter. It's the amazing adaptations and behaviors that make the naked mole rat a creature of beauty.

What the heck is a Naked Mole Rat?

One could argue that naked mole rats are the strangest mammals on Earth. But that's a matter of opinion, right? Let's look at them more closely so you can decide for yourself. Naked mole rats are not moles, nor are they rats. They are burrowing rodents that live in East Africa. This in itself is not unusual. After all, there are plenty of burrowing rodents, such as gophers, kangaroo rats, prairie dogs, and woodchucks.

But... naked mole rats are unique in a number of ways. The most striking is their social structure. Naked mole rats (and one other species of mole rat) are the ONLY mammal species that are eusocial. This is a type of social structure in which the adults live in groups and work together to care for the young, and only certain females (queens) are allowed to give birth. If you're thinking that's the way some ants, termites, bees, and wasps live, you're right. Those insects are eusocial. But there are no other mammals that are eusocial.

Amazing facts about Naked Mole Rats

Let's talk more about this eusocial thing. Hold on to your socks, because these amazing facts will just about knock them off! These creatures live in underground colonies, and when the queen dies, the dominant females basically start a war in order to choose which one will have the honor of being the new queen. As an example of how brutal this is, a captive colony of naked mole rats at the Smithsonian National Zoo needed a new queen, and during the selection process the number of adults was reduced from 17 to 13. The winning female in this case weighed 81 grams, while the closest competitor weighed only 55 grams. I guess size does matter.

Once a female becomes a queen, she starts having litters right away. Her first litter may have as few as two or three pups (each weighing less than a penny). But she'll get pregnant over and over, and each pregnancy will stretch her spine out a little more (seriously) until she can have room inside for up to 28 pups!

By the way, naked mole rats sleep in big, writhing piles (to help keep warm). That's why the pups in the photo above are piled with adults. One of those adults is the queen, the only one that will suckle the pups.

So, the queen nurses the pups until they are ready for solid food. At that point, the other adults in the colony take over care of the pups. They do this by feeding their poop to the pups! Yep, that's right. The adults produce a special kind of poop called cecotrope. This stuff is in the form of solid, yummy pellets that are full of good nutrients, as well as bacteria that the pups need in their guts to help them digest food as they grow older.

Check out this video on Naked Mole Rats

Let's take a look at the different roles in a naked mole rat colony. As stated above, there is one queen. And only one to three males reproduce with the queen. The other adults are called workers, and they are all sterile. The smaller workers typically gather food and take care of the nest. The larger workers are kind of like soldiers... if the burrow is attacked (by a snake looking for a snack, for example), these larger workers will defend the nest. In fact, they have been seen piling up at the entrance to block a snake from getting to the queen. This means that some of these soldiers might get eaten, thus sacrificing themselves for the queen. Wow.

All the workers, no matter their size, work together to take care of the pups.

As mentioned, other non-queen females in the colony are sterile. Amazingly, if the queen dies or is removed, some of the other females start producing certain hormones that make them fertile. And then they fight each other to become the queen. It is thought that the queen somehow suppresses fertility in all the other females in the colony. Again, wow!

Below is a pregnant queen:

Here's another way mole rats are different from ALL other mammals: They are ectothermic. That means they are essentially cold-blooded. They do not produce heat internally, like other mammals do. Instead of regulating their temperature internally, they regulate it by changing their behavior. To stay warm, they sleep in restless, always-moving piles of mole rats. When they're hot, they move down to the deeper levels of the burrow, and when they're cold, they move up closer to the surface, which is warmed by the sun.

Naked mole rats are extremely well adapted to the low-oxygen environment of their burrows. They can go without any oxygen at all for 18 minutes with no negative effects! And they can carry on with their normal activities for five hours breathing air that has only 5% oxygen (the normal oxygen level of the atmosphere of Earth is just under 21%).

Naked mole rats, quite literally, feel no pain in their skin. This is because their skin lacks neurotransmitters. This is thought to be an adaptation to living in conditions with extremely high levels of carbon dioxide (they use up the oxygen in their burrows and end up breathing lots of CO2). When breathing high CO2 levels, acid builds up in the tissues, which normally would cause pain.

Naked mole rats don't drink water. They get all the moisture they need from the food they eat (the underground parts of plants, like roots and tubers).

A colony may include 75 to 80 individuals, and one colony's burrow system can include two to three miles (3-5 km) of tunnels. They dig these tunnels entirely with their teeth! Impressive, considering they don't even have dental insurance. Their lips seal closed behind their teeth, to keep the dirt out of their mouths. A whopping 25% of their muscle weight is the muscles involved with closing their mouths as they dig. If that were true for a human, our jaw muscles would be the size of all the muscles in one of our legs.

Below is a photo of naked mole rats digging cooperatively. This is called a digging chain.

Naked mole rats live longer than any other rodents, up to 32 years! Most rodents this small (3 to 4 inches long, or 8 to 10 cm) live only a few years. Here's the weird thing about this: studies show that the mortality rate of these animals does NOT increase as they age. You may want to read that sentence again. They do NOT have more of a tendency to die as they grow older. In other words, they do not really age the way people do. They maintain a healthy heart and vascular system throughout their lives. And they are highly resistant to cancer. Pretty impressive, huh?

I'll finish with a cartoon from Lindsey Leigh that kind of summarizes (in a humorous way) the life of a mole rat colony.

So, the Naked Mole Rat deserves a place in the C.A.H.O.F.
(Copacetic Animal Hall of Fame).

FUN FACT: The word copacetic is one of those rare words for which the origin is simply unknown. It is used almost exclusively in North America, and sources sometimes attribute it to Louisiana French, or to Italian, or even to Hebrew, among other possible origins. But the truth is, no one knows for sure. It's also unusual because it is not considered slang in its modern usage. The word means completely satisfactory, just fine, or excellent. So, copacetic is, more or less, another way to say awesome!

Photo Credits:
Naked Mole Rat #1 - Meghan Murphy, Smithsonian’s National Zoo
Naked Mole Rats with Pups - Liberty Science Center
Pregnant Naked Mole Rat - The Japan Times
Naked Mole Rat Digging Chain - Justin O’Riain via ResearchGate
Naked Mole Rat Cartoon - Lindsey Leigh via ScienceFocus