Biologist Sara Weinstein, a Smithsonian-Mpala postdoctoral fellow at the University of Utah in Salt Lake City, and her colleagues saw African crested rats in Kenya chewing poisonous tree bark, and combing the toxin into specialized hairs on their coats, reports CBC’s Quirks & Quarks. Their study confirmed an older hypothesis that the rats are 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. 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 result in heart failure for most animals that come into contact with it. After the rat chews on the toxic bark, it spreads its 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 including leopards and hyenas that biting would be unwise.
