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Poisonous rats have a secret, softer side of their personality: NPR



The African crested rat is the only mammal known to sequester deadly plant toxins.

Stephanie Higgins


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Stephanie Higgins

The African crested rat is the only mammal known to sequester deadly plant toxins.

Stephanie Higgins

A poisonous rat licking deadly toxins on its own fur sounds like a kind of compound nightmare species. But these creatures are real, and scientists now say that they are also unexpectedly loving – at least of their own kind.

To be predators, the African crested rat, Lophiomys imhausi, are problems. They live in wooded areas on the eastern side of the continent, and people who have long known how to avoid these elusive black and white rodents.

“If a dog tried to attack them, the dogs would get sick and die. So this information has been circulating for a very long time,” said Sara Weinstein, a researcher at the Smithsonian Institution and the University of Utah who has worked with colleagues in Kenya to catch and study the rats.

The animals do not look like a typical city rat at all. “They’re actually the size of a small skunk,” she says. “A lot of it is fluff. They’re pretty fuzzy.” Like a skunk, these creatures have black and white markings that can serve as a warning. When the animal is threatened, it flares the fur to expose black and white stripes on its flanks.

Excitingly, these flanks have rows of weird hairs. They are much thicker than normal hair, Weinstein says, “and they have this really interesting honeycomb structure.”

The African crested rat sequesters venom from Acokanthera schimperi in specialized hairs, shown here along with typical hairs.

Sara Weinstein / Smithsonian National Zoo & Conservation Biology Institute


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Sara Weinstein / Smithsonian National Zoo & Conservation Biology Institute

The African crested rat sequesters venom from Acokanthera schimperi in specialized hairs, shown here along with typical hairs.

Sara Weinstein / Smithsonian National Zoo & Conservation Biology Institute

This structure appears to allow the hairs to act as a sponge to absorb toxins that the rat receives from a plant and consciously applies to its own body.

It has been known since 2011 when a team of researchers reported that they had caught a crested rat and offered it a branch from the local Acokanthera changes tree, which is also known as the “poison willow tree.” It contains a toxin that is supposedly potent enough to kill an elephant when applied to an arrowhead. The researchers looked at how the rat chewed on the bark and mixed it with saliva. Then the animal took over its specialized hairs with the bad mix.

The discovery thrilled mammologists. “Basically, it’s the only known mammal to date, at least we know of, that co-absorbs toxins from a plant to make itself toxic,” says Adam Ferguson, a mammal expert at the Field Museum in Chicago, who says that he is obsessed with these rats.

Weinstein and her colleagues wanted to confirm that this unusual behavior seen in a single rat was actually prevalent in this species. They also wanted to check if this rat’s health was really unaffected by this poison.

The research team eventually managed to capture and observe 25 rats. IN Journal of Mammalogy, they say, about half of them chewed on the tree branches and applied poison to their hair.

“Every once in a while, they did it, but not always,” says Weinstein, who says what triggers a rat to anoint itself remains a mystery.

The behavior really did not seem to have any negative impact on the animals, which remained perfectly active and healthy inside their enclosures, she says, noting that “if I were to go out and start chewing on this tree, I would get incredibly sick and probably die. . “

The researchers had assumed that these rats lived alone as they are rarely seen and usually seen alone. Then by chance they caught a male and a female rat living in the same area.

But when their cages were next to each other, “they started making these really interesting exciting vocalizations that we had never heard before,” Weinstein says.

The African crested rat was long considered to be solitary. A new study revealed an unexpectedly rich social life.

Stephanie Higgins


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Stephanie Higgins

The African crested rat was long considered to be solitary. A new study revealed an unexpectedly rich social life.

Stephanie Higgins

It certainly looked like two knew each other and wanted to be together.

When the two rats were placed in the same enclosure, “they began to care for each other, and they went into the nest box together,” Weinstein says, “which completely changed the way we thought about these animals and their behavior.”

From this point on, back and forth, if they caught an animal somewhere, they would set up other traps to try to trap more – and they often did. Now, scientists believe that the creatures can live in pairs and their cubs can stay with them for a long time.

“This latest paper is a very nice piece of work,” said Jonathan Kingdon, a zoologist at the University of Oxford who led the team that first observed a rat chewing bark and using poison.

After a childhood spent growing up in East Africa, Kingdon was familiar with these creatures to be able to describe them in the 1974 opus he wrote about African mammals. Still, he says there are many unanswered questions that “scream for attention, especially the exact chemistry and evolutionary history of crested rat saliva.”

Ferguson says that this rat has long been almost “mythical, avoiding our understanding, and there has been speculation. But now we’re finally trying to figure out what’s really going on with this rat.”

He and some colleagues are working on sequencing the entire genome of African crested rats to try to understand what it is about their biological composition that allows them to gnaw randomly on such a super-toxic plant.

“This thing is unique,” Ferguson notes. “As mammologists and biologists and humans in general, we are obsessed with rare things.”


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