Posted on behalf of George Wigmore.
Of all the ways to poison a predator, the methods of the African Crested Rat (Lophiomys imhausi) must be one of the strangest. By inviting attackers to bite their striking crest of poison-filled hollow hairs, they condemn their assailant to a likely death, while making their escape. The work is published today in Proceedings of the Royal Society B.
Fritz Vollrath, from the University of Oxford, and colleagues found that the porcupine-like creature fills its uniquely adapted hairs with its saliva after chewing the bark of the deadly plant Acokanthera. The heart-stopping poison, ouabain, is also used in the poison arrows favoured by East African elephant hunters.
When threatened, the rat pulls its head back onto its shoulders, flaring its fur, and presenting the attacker with a striking black and white target, outlining a leaf-shaped area of poisonous hairs. The rat then begins acting aggressively to incite its attacker, daring it to bite the exposed area, and poisoning the predator in the process.
Descriptions of the symptoms mainly come from dogs, and have ranged from a lack of coordination and distress, to collapse and rapid death. But there have also been reports of its defence being surprisingly effective against larger predators like lions.
The rat’s ability to erect its fur not only lets it attack, but also enables the animal to apply the poison to the special hairs, which is rapidly absorbed. But when relaxed, its long grey fur protects the poison from the elements, while also keeping it warm.
But besides its poison hair, the rat also has other adaptations to allow it to survive being chewed on by its enemies, including a tough, dense skin and a reinforced skull, similar to the armoured head of a turtle.
Although hedgehogs have been known to apply toad venom to their spines to make them more painful, its effects are not lethal. This makes the African Crested rat the only known mammal to display this unique and powerful defence.
Image: Crested Rat / Susannah Rouse