Rat 'poisons' fur to warn predators
Published 03/08/2011 | 00:10
A species of rat coats itself in deadly toxin that it obtains by gnawing on a poisonous tree, scientists have discovered.
The Crested Rat, Lophiomys imhausi, from East Africa, is the first mammal known to acquire lethal toxin from a plant.
To protect itself from predators, the creature chews the roots and bark of Acokanthera "poison arrow trees" to extract the poison ouabain. Bushmen in Kenya use the same poison to tip arrows which can fell an elephant.
In the case of the Crested Rat, the poison is absorbed into special lampwick-like hollow hairs on the animal's flanks.
When attacked, the rat puts on a dramatic fur-bristling display. Any predator that fails to get the message and takes a bite lives to regret it, or dies from heart failure.
Dogs have been known to collapse and die rapidly after biting a Crested Rat. Others that have survived an encounter shy away from the creature, according to local reports.
Dr Jonathan Kingdon, from Oxford University, co-author of the research published in the journal Proceedings of the Royal Society B, said: "At between 40 and 50cm long the Crested Rat looks quite innocuous as it clambers about in rocky, wooded valleys in Kenya and the Horn of Africa.
"But once disturbed or attacked the long fur on its flanks parts to expose a vivid black and white pattern around a leaf-shaped tract of peculiarly specialised hair, almost as if it is 'daring' a predator to take a bite of these poisoned hairs."
Many species of tree frog use the same trick of employing plant toxins to make them poisonous to predators, but the trait has never before been documented in a mammal.
The scientists observed a wild-caught rat chewing Acokanthera bark and roots, mixing the ouabain poison with its saliva and selectively applying the spittle to the hollow hairs. They were astonished by what they discovered when they examined the animal's poison hairs in the laboratory.