Amphibians
Rough-skinned Newt
Taricha granulosa · also called rough-skinned newt, Oregon newt
The rough-skinned newt is a small, unhurried, brown salamander from the damp forests of the Pacific Northwest, and it is one of the most poisonous animals in North America. Its skin is loaded with the same toxin that makes pufferfish deadly, in quantities that have killed a person — and the reason it is that toxic is a decades-long arms race with a single snake.
Overview
Rough-skinned newts live in moist coniferous forest and its ponds, lakes, and slow streams along the Pacific coast from southern Alaska to central California. They are among the most terrestrial of the western newts, often seen crossing forest trails and roads on damp days, and they breed in still or slow water in spring. Above they are a plain warty brown; beneath, a bright yellow-orange.
The toxin
The newt’s skin and organs contain tetrodotoxin (TTX) — the same neurotoxin found in pufferfish and the blue-ringed octopus. TTX blocks the sodium channels that nerves and muscles rely on, causing numbness, paralysis, and death by respiratory failure, with no antidote. The amount in one large newt, at the extreme, is estimated to be enough to kill more than a dozen adults if swallowed. Handling a newt with intact skin is safe — TTX does not cross unbroken human skin — but hands must be washed and eyes and mouth avoided.
A recorded death
In 1979, an Oregon man swallowed a rough-skinned newt on a dare after drinking. He developed the classic progression of TTX poisoning — tingling lips, spreading weakness and numbness — and died within hours despite hospital care. It is the clearest documented human fatality from a North American salamander.
An evolutionary arms race
Almost nothing can eat a Taricha newt — except the common garter snake, which in this region has evolved TTX-resistant nerve channels. Where resistant snakes are common, newts with higher toxin levels survive better, and the snakes evolve still more resistance, an escalating cycle that has pushed some newt populations to toxicity far beyond what any other predator would require. Newts in areas without resistant snakes are comparatively mild.
Warning
The newt advertises its poison with the unken reflex — arching head and tail upward to flash the bright belly — and with the belly colour itself.
Status
The rough-skinned newt is Least Concern, common and widespread, though local populations are vulnerable to wetland loss, road mortality, and introduced fish and bullfrogs that eat the larvae.
Rough-skinned Newt: common questions
How poisonous is a rough-skinned newt?
Extremely, if eaten. Its skin and organs contain tetrodotoxin, one of the most potent natural neurotoxins known, which blocks the nerve signals that muscles need to contract and causes numbness, paralysis, and death from respiratory failure. There is no antidote. The toxin content of a single large newt varies by population but at the high end is estimated to be enough to kill more than a dozen adults. It is not dangerous to handle a rough-skinned newt with intact skin — the toxin is not absorbed through unbroken human skin — but you must wash your hands afterwards and never handle one with a cut, or touch your eyes or mouth.
Did someone really die from swallowing one?
Yes. The best-documented case is from Oregon in 1979, when a 29-year-old man, after an evening of drinking, swallowed a rough-skinned newt on a dare from friends. Within a couple of hours he developed tingling around the mouth, then weakness and numbness spreading through his body; he was taken to hospital but deteriorated and died. His symptoms matched tetrodotoxin poisoning exactly. It remains the clearest recorded human fatality from a North American salamander.
Why is this newt so much more toxic than it needs to be?
It is locked in a coevolutionary arms race with a predator. In most of its range the common garter snake is the only animal that can eat rough-skinned newts, having evolved mutations in its nerve channels that make it resistant to tetrodotoxin. Where resistant snakes are common, natural selection has favoured newts with higher and higher toxin levels, and the snakes have in turn evolved greater resistance — an escalating cycle that has driven some newt populations to toxin levels far beyond what any other predator requires. In areas without resistant snakes, the newts are much less toxic.
How does the newt warn predators?
With colour and posture. The belly is bright yellow to orange, and when threatened the newt performs the unken reflex, bending its head and tail upward and sometimes closing its eyes, to display that warning colour prominently while hiding its duller back. A predator that has been sickened by a Taricha newt, or that instinctively avoids the pattern, leaves it alone. The bright underside is only shown when needed; at rest the newt's brown back keeps it inconspicuous on the forest floor.