This gorgeous African rat combs poison into its fur to deter predators
Researchers observed the rats chewing poison bark, and don't know how they are unaffected
Originally published on November 28, 2020.
A team of researchers has observed a unique behaviour in a mammal more typical of insects. Biologist Sara Weinstein and her colleagues saw African crested rats in Kenya chewing poisonous tree bark, and combing the toxin into specialized hairs on their coats.
Their study confirmed a older hypothesis that the rats are be sequestering toxins from the bark of a tree for defence against predators.
At first glance, the African crested rat looks like a cute, furry, grey rabbit with a little skunk mixed in. At about a kilo in mass, it's one of the larger and more attractive species of rat.
Weinstein is a Smithsonian-Mpala postdoctoral fellow at the University of Utah in Salt Lake City.
A mouthful of toxin
The rat harvests the toxin from a tree species called Acokanthera schimperi, known locally as the poison arrow tree, so named because its poison has long been used on the tips of hunting weapons. The bark contains an extremely potent toxin known as a cardenolide, similar to compounds found in monarch butterflies and cane toads.
The toxin affects muscle and nerves, and can ultimately result in heart failure for most animals that come into contact with it.
The crested rat chews on the leaves of the poison arrow tree. Sara Weinstein
Armed and dangerous
After the rat chews on the toxic bark, it spreads its now toxic saliva on specialized hollow and porous hairs that run in a band down the side of the animal. When the rat is threatened, these hairs stand up, revealing black and white stripes underneath. The researchers think these stripes serve to alert predators like leopards and hyenas that biting would be unwise.
One outstanding mystery for the researchers is how the rat avoids poisoning itself as it extracts the toxin from the tree bark.