Naked Mole Rat
As their name describes the naked mole rat lacks any fur on their body but they do have hairs between their toes and they have whiskers on their face. Their rotund body is covered with wrinkled skin that varies from pink to greyish. They have large incisors which are about the quarter of the size of their teeth that help to excavate tunnels. Their ears have no external portion.
An average naked mole rat measures 8-10cm (3-4in). The tail adds 8cm (3in) to their length. When a female becomes the queen (group leader) she will increase the length between each vertebrae making her longer.
Non dominant mole rats weigh 30g (1 ounce). The dominant pair may be almost double this at 50g (1.8 ounce).
Naked mole rats will feed upon a tuber that has grown in their burrow. This may be up to 1,000 times the weight of a mole rat. By only eating the inside of this tuber it can last the whole colony for up to a year as it continues to grow. They will also feed upon roots.
When eating they can use their long incisors like chopsticks by moving them independently. This also helps to keep these teeth short as they continuously grow.
They also eat their own feces. Due to the difficulty that they have digesting their food they follow it twice so that they can ingest all of the nutrients.
Their diet provides their moisture requirements meaning they do not drink.
30g (1 ounce)
50g (1.8 ounce)
Africa is the native home of the naked mole rat. Here they can be found in Kenya, Ethiopia and Somalia.
They will dig a tunnel in the desert areas and semi-arid grasslands where the colony can live. This tunnel system may stretch for up to 5km (3mi). These tunnels have a number of chambers which have different uses. One is for storing food, another for going to the toilet and one which acts as a mole rat nursery.
The queen devotes all of her time to breeding which can occur year round. A select group of males is allowed to mate with the queen.
70 days after mating the queen gives birth to an average of three to twelve pups. Some extraordinarily large litters may have up to twenty-eight pups. These pups feed from one of 12 nipples. This process may be repeated five times each year.
Within their burrow system is a nursery chamber where the pups stay. When it is born the small, helpless pup is carried to the nursery chamber by a worker. The mum will travel to this chamber to nurse the pups.
By two weeks old they begin to try solid food. The workers will also provide feces which they eat to provide the gut fauna that digests there food.
At three to four weeks old the pups are starting to perform working tasks.
Sexually maturity occurs at around one year old.
In naked mole rats all the colony are genetically similar due to lots of inbreeding.
Naked mole rats are one of only two eusocial mammals. This means they form colonies with a caste system. The 20-300 individuals are led by a dominant male and female with the rest divided between being workers and soldiers. To become queen females will often fight to the death. This role is defended vigorously and the queen often wanders the tunnels making it known that she is the boss by biting and pushing. When a female becomes the queen her hormones activate meaning that her ovaries begin to produce eggs so she can breed.
Workers acquire food, maintain tunnels and care for the pups. They are non-breeding and sterile.
To dig new tunnels the mole rats form a chain. The one at the front will dig using their teeth and the rest will use the hairs between their feet to brush the dirt out of the tunnel.
Soldiers will work to defend the colony from predators such as snakes or other mole rat colonies. They will use their large, sharp teeth to defend the colony. They may also form a pile which leaves a wall of gnashing teeth that the predator would need to fight through.
There are a range of social protocols observed in mole rat colonies. When two meet in a tunnel the smaller one will crouch down so the larger one can crawl over the top. So they can turn around they go to a tunnel junction and carry out a three point turn. To move through the tunnel they can also travel forward and backward.
When they get cold the mole rats come together in a ball so that they can share body heat.
Naked mole rats produce 18 different vocalizations which is the most of any rodent species.
Due to the lack of substance P in the skin of naked mole rats they do not feel pain when exposed to certain substances which would cause pain to other species. It is believed that this helps to deal with the build-up of carbon dioxide in their skin that leads to a build of acid in their muscle which would cause immense pain if they could feel it.
As a result of a special gene only seen in naked mole rats they are immune to cancer.
Their family name, Bathyergidae comes from Bathos a Greek word meaning depth and ergon that means worker.
Naked mole rats are also known as sand puppies.
They are one of the longest lived rodents on Earth.
This species does not have sweat glands meaning they cannot regulate their body temperature.
They have been observed chewing through concrete.
25% of their muscle mass is in the jaw.
Images taken from the Public Domain
Maree, S. & Faulkes, C. 2016. Heterocephalus glaber (errata version published in 2017). The IUCN Red List of Threatened Species 2016: e.T9987A115095455. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T9987A22184136.en. Downloaded on 19 May 2020.
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