Researchers discover Kenyan rat’s amazing juju tricks

National museums of Kenya head of mammology Bernard Agwanda holds a maned rat specimen at the museum on August 4. Phoebe Okall | NATION

Researchers have discovered strangely human behaviour in a rat found in Kenya and other parts of East Africa: it deliberately poisons its enemies.

In a trait common among humans, but rare in animals, the African crested rat collects poison from the msungu tree (msunguti or arrow poison tree) and coats itself in it.

Woe unto the predator that eats the witchdoctor rat, it soon dies of a heart attack.

Poison from the msungu tree is widely used, particularly by the Kamba who use it on arrows.

Researchers from the National Museums of Kenya, the Wildlife Conservation Society, and University of Oxford for the first time describe how the animal acquires, deploys and advertises the poison as a deterrent against its potential predators.

Dr Richard Agwanda of the National Museums of Kenya and one of the researchers said the rats studied were collected from Laikipia but that they are found all over the dry highlands of the country. The witchdoctor rat resembles a small porcupine.

“We observed the animals gnawing, chewing the roots and bark of the Acokanthera schimperi trees, known to be poisonous, then rub a coarse toxic gel onto the special hairs on its flanks to be delivered whenever the animal is bitten or mouthed by a predator,” Dr Agwanda said.

The study that also involved Margaret Kinnaird of the Mpala Research Station in Laikipia was published on Wednesday in the Proceedings of the Royal Society B.

Dogs which ate the rat lost coordination, frothed at the mouth and showed signs of general distress or collapsed and died quickly, apparently from heart failure.

Because of this, says lead researcher Jonathan Kingdom of the University of Oxford, in a statement from the Wildlife Conservation Society, people have always thought the rodent is poisonous, but their study shows that it has just found a way to poison predators.

When the researchers analysed its hairs, they found it to be loaded with a poisonous compound called ouabain from the tree bark.

This tree, which according to the Food and Agriculture Organisation is found in Machakos, Ongata-Rongai, Oloosaiyeti hill (Kajiado), Rumuruti (Laikipia), Loita, and Chepelion (north Baringo), has been used by local communities as arrow poison.

“A large enough dose triggers a fatal heart attack that can bring down even large animals like hippos and elephants,” Dr Agwanda says.

The compound ouabain, from the tree, says the study, has become famous as the weapon of choice by East African elephant hunters. Ironically the bark extract has also been in use as a clinical treatment against some heart failure complications.

The fruits are edible, but only when ripe. The Food and Agriculture Organisation says on its website: “Birds have been known to drop dead on sucking nectar from the flowers.”

Even though the crested rat looks like a porcupine, its hairs aren’t that sharp and they never actually pierce the mouths of its attackers.

But their open structure, says the statement, ensures that light contact is enough to send poison into a predator’s mouth.