A species of rat smears poison from a toxic tree onto its body to evade predators, scientists have discovered.

A team of Oxford University and East African scientists have published a report in Proceedings of the Royal Society B which details how the East African Crested Rat, or Lophiomys imhausi, gnaws the bark of Arrow Trees to get the poison, before smearing its saliva onto it tail hairs, near the base of its spine.

Jonathan Kingdon, from Oxford University's Department of Zoology and an author of the paper, said: "We observed the rat gnawing Poison-arrow tree bark directly from the plant, chewing it and then deliberately slathering the resulting mixture onto its specialised flank hairs. These hairs are designed to rapidly absorb the poisonous mixture, acting like a lamp wick."

The hairs are positioned close to the rat's head, neck and thorax, which are protected by shields of bone, a reinforced backbone and tough skin allowing the rat to evade all but the sharpest of bites.

The poison, called Ouabain, is a heart-stopping cardiac glycoside which has been used by doctors for centuries to stimulate weak hearts.

The Crested Rat appears to be immune to the poison. Research into the chemistry and genetics of the Crested Rat's use of the poison may lead to new medicines for humans.

A report of the research, entitled A Poisonous Surprise Under The Coat Of The African Crested Rat, is published this week in Proceedings of the Royal Society B.

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