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African crested rats They are fluff balls the size of a rabbit with endearing faces and a feline purr. But they are also highly poisonous, their fur is loaded with a toxin so powerful that only a few milligrams are lethal enough to kill a human.
Rats do not produce poison on their own. Rather, they borrow it from a poisonous plant by chewing on the bark, mixing the toxin with their saliva, and then preparing the lethal fluid into strips of specialized hairs on their flanks, a new study shows.
Some species of mammals, such as shrews, moles, and vampire bats, possess toxic saliva, while slow loris – the only poisonous primate – he makes his poison at home by mixing saliva with a discharge from his armpits. But the crested ratLophiomys imhausi) is the only mammal that obtains its protection against poison directly from plants.
Related: Photos: The Poisonous Creatures of North America’s Deserts
Crested rats’ bodies are about 9 to 14 inches (225 to 360 millimeters) long and inhabit forests in Ethiopia, Kenya, Somalia, Sudan, Tanzania and Uganda, according to Animal diversity website (ADW), a biodiversity database maintained by the University of Michigan Museum of Zoology. Rats were first described in 1867 and were long suspected of being poisonous. But they were so difficult to catch or observe that little was known about their habits, or where their venom came from, researchers reported Nov.17 in the Mammalogy’s Diary.
In 2011, biologists proposed that rats extracted their venom by chewing on the bark of the poison arrow tree (Acokanthera changes) and then applied the toxic substance by licking specialized hairs that rodents display when threatened. This tree bark contains cardenolides, compounds that are also found in foxglove (Digitalis purpurea) and that they are highly toxic to most mammals. Very small doses of cardenolides are used in heart Medications such as digitalis to correct arrhythmia, but larger amounts can cause vomiting, seizures, shortness of breath, and cardiac arrest. Oral contact with the venom-stained hairs of rats can be fatal, and the dogs have died after attacking the crested rats, the scientists wrote.
But research from 2011 described bark chewing and fur licking in a single rat, so researchers didn’t know how widespread this behavior was in the species, Denise Dearing, co-author of the new study and Distinguished Professor of Biological Sciences at the University of Utah, said in a statement.
For the new study, the researchers captured 25 rats in Kenya and temporarily held them in captivity, installed cameras in the animals’ enclosures, and analyzed nearly 1,000 hours of images of the rat’s behavior: 447 hours during the day and 525 hours at night. They observed 10 rats chewing the bark of A. changes, They applied toxin-laden saliva to their skin and did not appear to be affected by the venom, according to the study. Crested rats have “an unusual four-chamber stomach with a dense bacterial community,” so it’s possible for gut microbes to break down the cardenolides and prevent the toxins from making the rats sick, the study authors reported.
The scientists were also surprised to learn that the rats, once thought to be solitary, lived monogamously in male-female pairs, spending more than 50% of their time together and communicating with a variety of sounds including squeaks and purrs.
As the crested rat is rarely seen in the wild, scientists are still unsure of the rat population number and conservation status. But with humans increasingly invading and reshaping rat forest homes, the risks to animals have increased over the past decade, said Bernard Agwanda, Curator of Mammals at the Museums of Kenya and co-author of this study and of the 2011.
“We are looking at a wide range of issues influenced by habitat change,” he explained. “We need to understand how that affects their survival.”
Originally posted on Live Science.
