Giant African Rat Kills With Poisonous Mohawk

thebchuckster writes "The African crested rat has been known to kill local dogs, but researchers have just figured out how. After eating the 'poison-arrow plant,' the over-sized rodent stores its poison-laced spit in special hollow hairs in its mohawk. Then, when a predator grabs the rat, the animal gets stung with the poison and spit-tipped hairs which can sicken and kill."

Comments

How did this evolve?

[improfane]

It does make you wonder how something so specific could evolve, the relationship between a poisonous plant and then the distribution mechanism.

I know that when I eat certain herbs, I sweat them out and smell strongly of that herb whereas other people I know are fine. I wouldn't be surprised if that is related, the rats that could not sweat out the chemicals died, those that could survived, the ones who sweated through barbs fared even better. Do animals that disperse poison even know it's a defensive mechanism?

How can they evolve that knowledge? Or is it aggression that is evolved too? A poisonous rat that is passive will probably not survive (it might still get eaten if it kills its predator) whereas one that is aggressive can attack its predator before it eats it.

What do you think?

Re:How did this evolve?

[Chris Burke]

Polar bear fur isn't hollow, but it is transparent, and directs sunlight down to the bear's skin like a coat of fiber optic cables, which is basically what they are.

But yeah, this isn't that unusual. Chewing and grooming are normal behaviors for rats. The hairs could have evolved for any number of reasons, and may have been quite different, maybe just specialized whiskers, before the poison plant made predator-poisoning the main selective pressure.

There's other cases of this kind of thing. For example, hummingbirds and the flowers they feed from will often undergo runaway evolution where the hummer's bill will be specialized to feed on the flower's specialized form that only the hummer's bill will fit. Even more amazing, there's a species on a Caribbean island where the males and females aren't just different in plumage, but also very different in bill shape which is unusual. Each of the two sexes feeds exclusively from two different but closely related species of flower.

The theory was that when the hummers first arrived on the island, there was only one species of flower, and the more aggressive males monopolized the flowers that had the highest nectar output while the females were stuck with the ones with lesser output. The result was that the higher output plants were cross-pollinated by the males while the lower output plants were pollinated by the females, setting the stage for the two populations of flowers to begin diverging into separate species, and for each sex of hummer to follow.

I dunno, I thought that was neat.