London, Aug 4 (IANS) African crested rat could be predators' nightmare, because it applies a deadly plant toxin to sponge-like hairs on its sides to keep them at bay, says a research.

The toxin called ouabain comes from Acokanthera tree, the same source used by East African hunters for poisoning arrows. It is the only known instance of a mammal acquiring a poison from a plant for protection.

The discovery was made by Jonathan Kingdon and colleagues from the National Museums of Kenya, the Wildlife Conservation Society, and the University of Oxford, the journal Proceedings of the Royal Society B reports.

"The African crested rat is a fascinating example of how a species can evolve a unique set of defences in response to pressure from predators," said Tim O'Brien, senior scientist of the Wildlife Conservation Society and study co-author.

Scientists have long suspected that the rodent is poisonous, due to the its specialised behaviour, exposing a black-and-white colouration on its flanks when threatened by predators, according to a Wildlife statement.

Instead of producing poison itself -- as is the case with poisonous mammals such as the platypus and solenodon -- the African crested rat finds its toxin in tree bark.

Researchers confirmed the hypothesis by presenting a wild rat with branches and roots of the Acokanthera tree. It proceeded to gnaw and chew the bark (avoiding the leaves and fruit).