The deadly secret of a rat that kills lions and jackals has at last been revealed.
Unlike some mammals that produce their own toxins, the African crested rat is the first known to protect itself by daubing its fur with poisons from plants.
The same lethal toxins are used by African tribal hunters to coat their arrow-tips.
Suspecting that Lophiomys imhausi may obtain toxins from chewing on the bark of the poison-arrow plant, acokanthera, Fritz Vollrath of the University of Oxford and his team offered some to a captive animal.
Over the course of a week, it periodically chewed the bark then smeared its saliva over a section of short hairs that lies along its flank, hidden inside its fur.
Placing the hairs under a microscope revealed that their surface is perforated. Each also contains fibres at its core, allowing it to soak up the toxins and store them.
Vollrath says the findings tally with reports that when attacked, the rat stands its ground, parts its fur to reveal the stripe of poisonous hair, and invites the aggressor to bite its flank.
Aggressors who do go in for the kill have been seen to shrink back, froth at the mouth and often collapse and die, apparently from heart failure.
The rats are also known to have abnormally thick skins and skulls, which probably evolved so that they could survive attacks until the poison kicks in. They have also – clearly – evolved immunity to the toxins.
Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2011.1169
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