Naked Mole-Rats: Strange Discoveries About an Unusual Animal

Updated on April 25, 2017
AliciaC profile image

Linda Crampton is a writer and teacher with an honors degree in biology. She loves to study nature and write about animals and plants.

A female naked mole-rat
A female naked mole-rat | Source

Weird and Fascinating Rodents

Naked mole-rats are burrowing rodents with a strange appearance and even stranger features. A new discovery has added to their weirdness. Scientists already knew that the animals are resistant to some kinds of pain and very rarely get cancer. Now researchers have found that the animals can survive for up to eighteen minutes in an environment without oxygen. Given that rodents are mammals like us, the mole-rat's features are intriguing. Understanding its abilities could be useful with respect to understanding human biology and perhaps even in helping to treat some of our health problems.

World's Weirdest: Naked Mole-Rats

Physical Appearance

Naked mole-rats (Heterocephalus glaber) live in the deserts of East Africa in large, underground colonies. They are neither moles nor rats, but they are rodents. The animals have grey to pink skin that is wrinkled and fits loosely on their body. The skin bears very little hair. The animals aren't completely naked, however. They have sensory bristles on their skin as well as fine hairs.

The body of a naked mole-rat has a tubular shape. Although the eyes are small, the animals aren't blind as is sometimes claimed. They do have poor vision, though. The Cornell University professor in the video below says that the eyes are used only to distinguish light from dark. There is no external ear flap, but there is a hole on the side of the head to allow sound waves to enter the ear.

The animals have two long upper incisors that protrude through their lip just below their nostril. They also have two protruding lower incisors. Since the teeth are outside the mouth, the animal can keep its lips closed while digging a tunnel. This stops it from swallowing soil.

Naked mole-rats are more closely related to guinea pigs and porcupines than to rats and moles.

In this photo of a captive naked mole-rat eating, the upper and lower incisors can be clearly seen.
In this photo of a captive naked mole-rat eating, the upper and lower incisors can be clearly seen. | Source

Life Underground

The mole-rat colony may be very large. Researchers say that there may be from twenty to three hundred animals in the group, although seventy to eighty animals is the most common colony size. The burrow may extend over a large area and is organized into different chambers, or "rooms". These have specific purposes, including serving as a nursery, a food storage area, a sleeping area, or a toilet.

The animals feed on underground roots and tubers and get all the water that they need from their food. They also eat their poop in order to extract extra nutrition from any undigested food. The rodents role in the poop in addition to eating it, which gives them the typical smell of the colony. This enables the animals to identify colony members. The use of smell is important, since the rodents have bad vision and live in a dark area.

Naked mole-rats are vocal animals and have good hearing. Researchers have discovered that they produce at least eighteen distinct vocalizations. Sound is an important method of communication for them. The animals that find food that can't be moved inform the other members of the colony about their discoveries via sound and behaviour. The rodents can run as fast backwards as forwards in their tunnels.

In order to create a new tunnel in their burrow, the mole-rats work cooperatively. They form a chain of animals. The first animal removes soil from an area and the others kick it backwards through the chain until the soil reaches the surface.

Naked Mole-Rat Information From a Cornell Professor

Organization of the Colony

The colony is ruled by the dominant female, or the queen. She is the only animal to breed. Her body becomes longer and larger once she becomes the queen, which enables her to contain more pups. If necessary, she fights to maintain her role in the colony.

The queen allows only two or three of the males to mate with her and is often said to give birth to up to twenty-seven pups at a time. The researcher in the video above says that the largest litter at Cornell contained thirty-three pups, however. The usual litter size is twelve to eighteen pups. The gestation period is about seventy days. The queen may breed four to five times a year, which helps the colony to become very large.

The other members of the colony are known as workers or soldiers. They have specific jobs, such as feeding and caring for the queen, taking care of the pups, digging tunnels, searching for food, and protecting the colony from enemies. They work as a group to fight predatory snakes.

It's interesting that the mole-rat colony has a social organization that resembles that of a bee colony. The rodents and the insects are very different animals, yet they have each developed a similar way of life.

The bristles and hairs can be seen on the body of this naked mole-rat.
The bristles and hairs can be seen on the body of this naked mole-rat. | Source

Interesting and Surprising Facts About Naked Mole-Rats

  • The skin of adult naked mole-rats can't detect pain caused by acid or by capsaicin from hot peppers. The first ability could be very useful in tunnels filled with exhaled carbon dioxide, since the chemical reacts with water to form carbonic acid.
  • It's frequently claimed that the animals don't get cancer. It might be more accurate to say that they rarely get the disease, because at least two animals in captivity have developed conditions that at least resemble cancer. Whether the animals ever get the disease in the wild is unknown.
  • Unlike most other mammals, naked mole-rats don't regulate their internal body temperature very well. They are often said to be "cold-blooded", which means that their body temperature is approximately that of the environment. They need to huddle together on cold nights so that they stay warm.
  • Animals kept in captivity have been able to chew through concrete.
  • The animals have lived for as long as thirty-two years in captivity and stay agile as they age. Most rodents of similar size die when they are five years old or younger.

Mole-Rats Move a Carrot

Living Without Oxygen

The tunnels in the naked mole-rat colony have a low oxygen content and a high level of carbon dioxide, but this doesn't seem to bother the animals at all. Hypoxia is a condition in which an inadequate amount of oxygen reaches the tissues. This definition doesn't apply very well to naked mole-rats because even when the amount of oxygen in their bodies is low, they don't appear to experience any ill effects.

In April 2017, an amazing discovery was announced. A group of researchers reported that the naked mole-rats in their study survived for eighteen minutes with no oxygen at all in the environment. The animals lost consciousness and their heart and breathing rate slowed very significantly, but they didn't die. When oxygen was returned to their environment they recovered and behaved normally.

Mice kept in the oxygen-free environment died after a minute. All of the mole-rats survived for eighteen minutes. Three mole-rats left in the environment for longer were dead after thirty minutes. The topic of cruelty to animals could certainly be raised at this point, but if this unpleasant thought is ignored, the results of the experiment are very interesting.

The scientists also discovered that the mole-rats lived with no problems in air with only 5% oxygen. (Air normally contains close to 21% oxygen.) After five hours of watching the animals in the experimental chamber and seeing no effects of the low oxygen content, the scientists stopped the project and returned the animals to their habitat. In contrast, mice died after fifteen minutes in the low-oxygen atmosphere.

A Rodent Surprise

Fructose Metabolism

The researchers discovered that a key process in the mole-rats' metabolism changed when oxygen was absent. Humans and other mammals normally get energy from glucose. The complete, multistep process of producing energy from glucose requires oxygen, which is why we need to inhale the gas. When no oxygen was available, the mole-rats quickly switched to using fructose for energy. The fructose level in the rodents' blood rose and the amount in their brain and heart increased.

Mammals can obtain energy from fructose in the presence of oxygen. The mole-rats were able to obtain energy from fructose via a different process that didn't require oxygen, however. The amount of energy produced was enough to keep the rodents alive and apparently enough to prevent tissue damage for eighteen minutes. It wasn't enough to keep them conscious, however.

The research has attracted a great deal of attention. Scientists caution that there may be other factors responsible for the rodents' survival besides fructose use in the absence of oxygen, however. These factors may include a low body temperature compared to that of other mammals and a low metabolic rate. Still, many researchers are interested in the study results because they are so unusual for an animal.

The Great Naked Mole-Rat Escape

The Pacific Science Center in Seattle has a webcam that lets people look at the naked mole-rat exhibit from their home. The video above was made by the webcam and is slightly sped up. All of the animals that escaped from the habitat were returned safely to their home.

Possible Applications of the Research

The researchers studying fructose use in mole-rats think their discoveries might help humans. People who experience a heart attack or stroke often develop hypoxia immediately after the incident. The brain in particular needs a constant supply of oxygen so that it can produce energy. If it doesn't get this energy, its cells start to die. The production of energy from fructose without the need for oxygen might be helpful for preventing or reducing tissue damage after a stroke or heart attack. It might even save lives while patients are waiting for other treatments to work.

The researchers are currently investigating whether human cells have the ability to use fructose without oxygen. One of the scientists involved in the rodent research wonders whether deep-sea divers who hold their breath for a long time while hunting for pearls or while freediving have unknowingly triggered the system. This is pure speculation at the moment, but it's an interesting idea to consider.

It's possible that understanding the healthy aging of mole-rats and their resistance to pain and cancer may also be helpful to humans. Thinking about the features that may or might one day apply to humans is an interesting activity. The animals have some amazing and bizarre characteristics. They are fascinating creatures to study.

References

Questions & Answers

    © 2017 Linda Crampton

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      • AliciaC profile imageAUTHOR

        Linda Crampton 

        8 months ago from British Columbia, Canada

        Hi, Jon. Thanks for the comment. I agree that we need to know more details about the process. I'll watch out for scientific reports that aren't behind a paywall and add them as references if and when I find them.

      • Jon Richfield profile image

        Jon Richfield 

        8 months ago from South Africa

        Hi Linda,

        your writing is as impressive as usual, and the mole-rats are full of interest, as they have been ever since the work by Alexander, Sherman, and Jarvis since the early eighties, but one aspect bothers me here.

        The sources quoted here on metabolism in the absence of oxygen are at best incoherent and as far as I can tell inaccurate. I accept that the animals tolerate startling oxygen deprivation, and that they have a complex of adaptations to underground levels of oxygen, but their statements on fructose and glycolysis simply make no sense. The biochemists/physiologists they tried to quote probably knew what they were talking about, but interpreters for the public have messed it up badly.

        Firstly, glycolysis needs no oxygen -- period. The process breaks down glucose (first having converted it to a fructose phosphate, by the way). Then it performs a few more steps that actually consume energy in the form of ATP molecules, then in the last three steps or so it breaks down some energy-rich products, producing in the end a profit of two ATP molecules per glucose molecule.

        So far NO oxygen involved, whether from glucose OR fructose, right?

        Fructose also can enter the pathway directly and perhaps more actively by a shortcut, as a different phosphate, but using neither more nor less oxygen, and producing much the same pyruvate, lactate etc as before.

        Where oxygen comes into the drama is after the glycolysis as the pyruvate is converted into an acetyl residue that starts the citric acid cycle and produces lots of energy and CO2 USING LOTS of O2. This is the same for glucose and fructose.

        Not knowing the mole-rat details, I can't take it much further now, but I suspect that the benefit might lie in that glycolysis is more important as a molecular process that affects a lot of other physiology and depends on processes that cannot carry on in the absence of O2. Splitting the fructose directly might involve fewer associated processes harmfully.

        But if you have any university contacts more familiar with that work, I recommend that you check the details with them.

        All the best

        Jon

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        9 months ago from British Columbia, Canada

        I can understand why you would say this, Tamara. Close-up photos of a naked mole-rat's face are very interesting!

      • Rhyme Vine Poetry profile image

        Yancosky 

        9 months ago from Uninhabited Regions

        Yikes, these are terrifying!

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        12 months ago from British Columbia, Canada

        Hi, Jackie. I've never thought of a naked mole-rat looking like a cat! It's an interesting idea. I hope studying the animals does lead to ways to help humans.

      • Jackie Lynnley profile image

        Jackie Lynnley 

        12 months ago from The Beautiful South

        So interesting and yes, weird! Looks kind of like the cat, huh? Perhaps they will bring a break through in lung disease to find a cure.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        That's okay, John. I agree with you - it's still an amazing ability!

      • Jodah profile image

        John Hansen 

        15 months ago from Queensland Australia

        Sorry, Linda. You are right.. 18 minutes I meant. Still amazing.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Thank you very much, John. I think that the animals are very interesting creatures, too, although they can actually survive only eighteen minutes without oxygen. That's amazing, though. They are impressive rodents.

      • Jodah profile image

        John Hansen 

        15 months ago from Queensland Australia

        Linda, this is a terrific article. I find the naked mole rats a very interesting creature. Fancy surviving 18 hours without oxygen, and being able to run backwards as fast as forward. Also interesting that their colony works in a similar way to bees.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, Dora. Biology is certainly fascinating! Thank you very much for the comment. I appreciate it a great deal.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Thank you, Peggy. I appreciate your kind comment and the share very much.

      • MsDora profile image

        Dora Weithers 

        15 months ago from The Caribbean

        I am still amazed at the ability of humans to figure out all this stuff about these strange creatures. And Linda, I applaud you for these presentations in which you give such detail and manage to keep readers interested. Great job!

      • Peggy W profile image

        Peggy Woods 

        15 months ago from Houston, Texas

        What a terrific article you wrote Linda. I learned so much that I might never have known about these interesting creatures. The study of these curious creatures will perhaps bring about scientific discoveries that might help medical as well as space exploration in the future. Your articles are always worth reading! Sharing this!

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, Manatita. Thank you for the visit. I always appreciate your comments.

      • manatita44 profile image

        manatita44 

        15 months ago from london

        Very intriguing piece. Only goes to show the divine works of God.

        Well written as always and carefully put together. I enjoyed the videos. I hope that they can help us some day. Nice Hub, Linda.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, Devika. Yes, the animals are certainly strange! Thank you for the visit.

      • DDE profile image

        Devika Primić 

        15 months ago from Dubrovnik, Croatia

        Weird and also interesting as I have not heard of such facts. These creatures are strange.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, Ann. My only experience with guinea pigs was when I took care of two animals from my school over the summer. I noticed the sounds that they make, too. Thank you very much for the comment.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, June. It's very interesting to hear about other people's reactions to the animals. Thanks for the comment and for sharing your opinion. I suspect that many people agree with your feelings about the animal's appearance!

      • annart profile image

        Ann Carr 

        15 months ago from SW England

        What fascinating creatures and you've told us so much about them here in this detailed article.

        Interesting that they're related to the guinea pig. They make lots of noises for communication too which I didn't know about until my daughter got two lately.

        The cancer and pain resistance is amazing too. Great stuff!

        Ann

      • Kailua-KonaGirl profile image

        June Parker 

        15 months ago from New York

        These are the most disgusting looking critters I have ever seen! Granted, I can understand your interest in them, and you have written a fascinating, well-researched article about them, but man oh man are they are gross to look at.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Thank you for the visit, Paula. The results of your survey are interesting! I think it's worth knowing something about the rodents, even though some people think they're ugly.

      • fpherj48 profile image

        Paula 

        15 months ago from Beautiful Upstate New York

        Can't believe this is all brand new info to me! I truly enjoy learning little known facts. The first 3 people I questioned had never heard of these strange-looking creatures either! Thank you for making us just a little more informed than we were yesterday!

        I do believe these critters may be very beneficial to new discoveries. Oh, I hate to say it, but my goodness they are terribly ugly little things!! Wow, hope they're not listening to us!! LOL

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, Mary. It's interesting that a little creature like the naked mole-rat could be helpful to humans. As you say, biologists always seem to have interesting discoveries to show us!

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Thank you so much, Larry. I appreciate your comment.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Thanks, RoadMonkey. The animal certainly has some very interesting features!

      • Blond Logic profile image

        Mary Wickison 

        15 months ago from Brazil

        The whole subject of biology is fascinating and always seems to have an endless supply of discoveries.

        The usefulness of this information about living in a low oxygen environment to using fructose to counteract the problem is fascinating. The potential benefits to medical science and mankind could be immense.

        Thanks for bringing it to our attention.

      • Larry Rankin profile image

        Larry Rankin 

        15 months ago from Oklahoma

        I think that may be the least adorable thing I've ever saw, lol.

        I always enjoy learning from your articles. I really appreciate your writing.

      • RoadMonkey profile image

        RoadMonkey 

        15 months ago

        Fascinating article. Very interesting to hear that their teeth are outside their lips!

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Thanks for commenting and for sharing the information, Penny. I've never heard of Kim Possible before. It's interesting to hear that a naked mole-rat was a character in a cartoon.

      • Penny Sebring profile image

        Penny Sebring 

        15 months ago from Fort Collins

        Fascinating little critters aren't they? Naked mole rats were one of my daughter's favorites when she was little, thanks to KimPossible. The real thing is much more interesting than the cartoon though.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, Louise. They definitely are strange creatures. I agree with you about the teeth, too. They are impressive structures!

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Thank you very much, Buildreps! I appreciate your visit and your interesting comment.

      • Coffeequeeen profile image

        Louise Powles 

        15 months ago from Norfolk, England

        Goodness, what strange little creatures. I've never heard of these before! Their gnashers are huge!

      • Buildreps profile image

        Buildreps 

        15 months ago from Europe

        Very interesting article as always, Alicia. You explained it brilliantly how the process of switching from oxygen consuming metabolism to a non-oxygen consuming metabolism works. I loved to read it!

        I have somewhere the feeling that ugliness and survival skills go hand in hand. Or maybe is it caused because these animals are purely functional and beauty plays no role, they are blind, sort of.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, Bill. I certainly understand your point of view! I find their appearance interesting rather than gross, but I can understand why not everyone shares my opinion. Thanks for the visit.

      • AliciaC profile imageAUTHOR

        Linda Crampton 

        15 months ago from British Columbia, Canada

        Hi, Flourish. I love biology and learning about new discoveries, but like you, one aspect of the research that upsets me is the treatment of animals. I have read that the use of stem cells is being investigated as a way to reduce some kinds of animal testing. I hope this change happens very soon. Thanks for the comment.

      • billybuc profile image

        Bill Holland 

        15 months ago from Olympia, WA

        Okay, it's confession time, Linda: I love animals, but these little creatures gross me out! There, I've said it. LOL Great information, fascinating, really, but they still gross me out.

      • FlourishAnyway profile image

        FlourishAnyway 

        15 months ago from USA

        Holy moley this was a good article. The facts about chewing through concrete and pain endurance are very interesting. I really hope that there is a special place in hell for those scientists who exposed them to such awful experiments. Your article was excellent though. Thoroughly fascinating. They are so ugly they are cute. Funny about the rolling in poop and eating it. Makes me wonder what they do with their dead.

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