Meet the 'sabre-toothed sausage'

By Rebecca Morelle
Science reporter, BBC News

  • Published

"They look a bit like a sabre-toothed sausage," says Dr Chris Faulkes, as we enter the naked mole rat laboratory at Queen Mary, University of London.

Scuttling around in a maze of tubes are dozens of small rodents. They appear to be hairless, covered with wrinkly, pink skin and they have beady, black eyes. But the thing that really catches your attention is their enormous, protruding teeth.

At first glance, it's clear that Dr Faulkes' description is spot on.

"It's a really, really bizarre looking animal," admits the scientist, who has spent the past 20 years studying naked mole rats.

These rodents, which belong to the African mole rat family, are found in parts of Kenya, Ethiopia and Somalia.

They live in huge underground burrows, which goes some way to explaining why these creatures look like they do - they use their giant teeth to help them dig.

Dr Faulkes says: "They are amazingly well adapted to living underground."

Busy as a bee

But it isn't just their unusual appearance that attracts attention: their behaviour is about as strange as it gets in the mammalian world.

For a start, these little creatures live in huge groups. On average, you will find colonies made up of 80-100 individuals, but sometimes they can grow to a 300-strong group.

More bizarre still is their social structure.

Dr Faulkes points to a mole rat that looks almost twice as large as any nearby. And it is clearly pushing around some of its punier companions.

"That's the queen," he says. "Even in these really huge colonies, there is only a single female that breeds. And she mates with one or two, or sometimes three, breeding males.

"And then the rest of the colony, of both sexes, have their reproduction suppressed and never ever breed."

But the sex-free mole rats have another job, he explains.

"The small ones tend to act as workers, so they carry out colony maintenance activities," says Dr Faulkes.

The larger animals seem to adopt a more defensive role, he adds, keeping predators, such as snakes, at bay.

And if this kind of set up sounds rather familiar, that's because it is.

Dr Faulkes explains: "They behave like the mammalian equivalent of a social insect - they have many, many similarities with bees, ants, wasps and termites."

Throw in on top of this the fact that naked mole rats also live for an unfeasibly long time for a small rodent - 30 years in captivity - and that they also seem to be resistant to cancer, so it is easy to see why scientists are so interested in them.

Image caption,
Could mole rats give us clues about monogamy?

"There are so many aspects of their biology that are extreme," says Dr Faulkes.

He, working with neuroscientist Professor Clive Coen, from King's College London, and zoologist Professor Nigel Bennett, from the University of Pretoria, has used this as the basis to find out what lies behind the naked mole rats' behaviour, and in turn, to start to look at how this might relate to other mammals - including humans.

And one way that they have been doing this is to compare naked mole rats with another member of the African mole rat family, the Cape mole rat.

Where the naked mole rat is a highly social animal and forms long-term social bonds, especially between the queen and her select suitors, the Cape mole rat is solitary and aggressive, and sexually, rather promiscuous.

Dr Faulkes says: "They represent both ends of the spectrum in sociability."

Earlier research carried out on voles had suggested that differences in the way that receptors for two hormones, oxytocin and vasopressin, were expressed in the brain could make a huge impact on social behaviour, including determining whether a species was likely to be monogamous or promiscuous.

So the team decided to look at whether these hormones could also be linked to the differences in behaviour between the two mole rat species.

Image caption,
The Cape mole rat is a solitary animal

Dr Faulkes explains: "We found that the naked mole rats and the Cape mole rats had substantially different patterns.

"The solitary, highly aggressive Cape mole rats had their oxytocin receptors distributed in a different part of the brain to the naked mole rats, while the naked mole rats' oxytocin receptors were found in the same region as monogamous voles."

He added: "This is really telling us that these kinds of systems of differing patterns of distribution for the oxytocin receptors are an important part of what underlies different kinds of social behaviour across mammals."

And while this research has focussed on mole rats, other research groups have been looking at the effects of these hormones on humans, including a recent study that suggested men who inhaled oxytocin became as empathetic as women.

Dr Faulkes says: "It seems even in humans that such changes can actually alter human reproductive behaviour, such as how stable relationships are.

"Some people have even linked mutations in the oxytocin receptor gene to certain types of autism."

Big questions

Image caption,
The mole rat could help us to answer many questions

But scientists are not just looking at social behaviour. They also think that naked mole rats could help us to sniff out answers to a whole host of questions linked to the human condition.

Some researchers are trying to find out whether the animals hold the key to longevity; others are looking at the clues they might give us in the fight against cancer; while some scientists want to see if they can help us to answer questions about reproduction and fertility.

Dr Faulkes says: "Although it might seem a bit of a stretch of the imagination to go from a naked mole rat to humans, the underlying biology is very, very similar.

"And they are just so unusual and there are so many aspects of their biology that are extreme that they could help us to extend our knowledge across so many species and disciplines."

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