How the Rough-Skinned Newt Defends Itself

the rough-skinned newt

Washington Department of Fish and Wildlife

A naturalist touring Australia is cautious. Unlike our neck of the woods, most snakes there are poisonous. Both jellyfish and a large bird can kill you. Even deadlier, though, is the blue-ringed octopus. A bite can be fatal in 90 minutes. What's our deadliest animal? It's not the black widow, not the rattler, but a newt. One rough-skinned newt divided up and eaten can kill 17 people. Oregon holds the record of death by newt.

So what do these octopi, newts and zombies have in common? They all have tetrodotoxin, a group of the world's strongest poisons. Haitians secretly added small amounts of puffer fish tetrodotoxin to meals that were then eaten by those who violated certain taboos. Victims were buried because they were dead or had very shallow breathing and weak heartbeats. The poisoners then dug up the survivors and fed them datura or jimson weed. When the drugs wore off, the victims believed that had died and therefore must serve their new masters.

The rough-skinned newt is the only landlubber with this tetrodotoxin, perhaps because it belongs to the oldest living family of salamanders, those closest to ancestors from the sea where other animals with this poison live. Bacteria within animals apparently make the toxin and the more recent land families probably lost these bacteria.

 

An arms race occurs between this newt and the common garter snake, with resistance to the poison and poison amounts similar in the same area but different when comparing two populations. Newts with just enough toxin survive to pass on their ability to make the toxin because garter snakes will vomit up live newts up to 85 minutes after eating them. Newts with too much toxin paralyze the snake before getting regurgitated.

Like all arms races, there’s a cost. It takes energy to make poison. Both the toxin and apparently the resistance to the toxin make garters more sluggish and so vulnerable to predators. So where snake predation is high, as apparently on Vancouver Island, both newt and snake signed a peace treaty; both poison amounts and resistance to the poison is low there.

When threatened the rough-skinned newt exposes its bright red-orange belly, a stop sign to would-be predators, a neon sign that says “eat me and you will be sorry.” So wash your hands after handling a newt and before poison gets in your eyes or mouth. And don’t eat a newt or anything bigger than your head!