A poisonous rat licking deadly toxins on its own fur sounds like some kind of fictional nightmare. But these creatures are real, and scientists now say they are also unexpectedly attached – at least to their own kind.
For potential predators, the African Crested Rat, Lophiomys imhausi, is a problem. They live in wooded areas in the eastern part of the continent and people there have long known that they are protected from these elusive black and white rodents.
“If a dog tries to attack them, the dogs will get sick and die. So this information has been spreading for a very long time,” said Sarah Weinstein, a researcher at the Smithsonian Institution and the University of Utah who has worked with colleagues in Kenya. to catch and study rats.
The animals do not look like a typical city rat at all. “They’re actually the size of small skunks,” she says. “A lot of them are fluffy. They’re pretty fuzzy.” Like skunks, these creatures have black and white markings that can serve as a warning. When the animal is threatened, it inflames its fur to expose black and white stripes on its hips.
Interestingly, these flanks have rows of strange hairs. They are much thicker than normal hair, says Weinstein, “and have this really interesting honeycomb structure.”
Sarah Weinstein / Smithsonian National Institute of Zoology and Conservation Biology
This structure appears to allow the hairs to act as a sponge to absorb the venom that the rat receives from the plant and deliberately applies to its own body.
This has been known since 2011, when a team of researchers reported that they had caught a rattlesnake and offered him a branch from the local Akokantera is changing a tree also known as the “poison arrow tree”. Contains a toxin that is said to be powerful enough to kill an elephant when applied to an arrowhead. The researchers observed the rat chewing the bark, mixing it with saliva. The animal then smeared its specialized hair with the unpleasant mixture.
The discovery excited mammologists. “Basically, this is the only mammal known so far, at least we know, that co-opted toxins from the plant to make it poisonous,” said Adam Ferguson, a mammalian expert at the Field Museum in Chicago, who said he was obsessed with these rats. .
Weinstein and her colleagues wanted to confirm that this unusual behavior, observed in a rat, is in fact widespread in this species. They also wanted to check if the rat’s health was really affected by this poison.
Eventually, the research team managed to capture and monitor 25 rats. IN Journal of Mammology, they say, about half of them chewed the branches of trees and applied poison to their hair.
“They did it from time to time, but not always,” says Weinstein, who says what causes a rat to be anointed remains a mystery.
The behavior really didn’t have a negative effect on the animals, which remained fully active and healthy in their enclosures, she says, noting that “if I had to go out there and start chewing this tree, I would get incredibly ill and probably die. “
The researchers had suggested that these rats lived a solitary life because they were rarely seen and were usually seen alone. Then they happened to catch a male and a female rat living in the same area.
When their cells were next to each other, “they started doing these really interesting purring vocals that we had never heard before,” Weinstein said.
It certainly seemed that the 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 entered the nest together,” says Weinstein, “which completely changed the way we thought about these animals and their behavior.”
From then on, if they caught an animal in one place, they would set other traps to try to catch more – and they often did. Researchers now believe that creatures can live in connected couples and their young can stay with them for a long time.
“This last article is a very good job,” said Jonathan Kingdon, a zoologist at Oxford University who leads the team that first observed a rat chewing bark and applying venom.
After a childhood spent growing up in East Africa, Kingdon was familiar enough with these creatures to be able to describe them in a 1974 opus he wrote on African mammals. Still, he says, there are many unanswered questions that “scream for attention, most notably the precise chemistry and evolutionary history of rat saliva.”
Ferguson says this rat has long been almost “mythical because it has escaped our understanding and there is speculation. But now we are finally trying to figure out what is really going on with this rat.”
He and some of his colleagues are working on the sequence of the entire genome of African rats to try to understand their biological composition, which allows them to carelessly gnaw on such a supertoxic plant.
“This thing is unique,” Ferguson said. “As mammologists and biologists, and people in general, we are obsessed with rare things.”