The rough-skinned newt, its toxin and the snake that eats it

A rough-skinned newt carries a defense that sounds like a rumor. The Animal Diversity Web, a University of Michigan database, says one newt holds enough toxin to kill several humans. A 2008 National Geographic blog post about a study by Charles Hanifin and colleagues puts it at 10 to 20 humans for the skin of a single newt. Most predators take the hint. One famous exception does not.

The newt is Taricha granulosa, a salamander of the Pacific coast. The toxin is tetrodotoxin, TTX for short, which blocks the sodium channels that nerves and muscles need to work. The exception is the common garter snake, which in some places has evolved resistance to TTX. Newt and snake have been pushing against each other ever since.

This article covers the newt itself, how the toxin works, how the newt avoids poisoning itself, and the arms race with garter snakes, including what the snakes pay for their resistance. It is not a guide to handling wild animals. Rough-skinned newts carry a potent toxin, so watch them from a distance and leave them alone.

Meet the rough-skinned newt

The Animal Diversity Web places the species along the Pacific coast from Santa Cruz County, California, to Juneau, Alaska, from sea level up to about 2,743 meters (9,000 feet), including Vancouver Island. The same source also lists isolated populations in Idaho and Montana, and says the Idaho population, at least, is probably introduced. Adults measure about 12.7 to 21.6 cm (5 to 8.5 inches). The back is dark, the belly is orange to yellow-orange, and the grainy skin gives the animal its name. Breeding males turn smoother and lighter, with bigger tail crests.

Despite being a newt, it spends most of its time on land, hiding under rotting wood. It heads for still or slow water to breed. The same source says the newts probably use celestial cues and smell to find their way between land and breeding sites. The spotted salamander has its own famous trip to the breeding pool.

How the toxin works

Hanifin and William Gilly describe the mechanism in a 2014 paper in Evolution. TTX binds to the outer pore of voltage-gated sodium channels, the gates that let sodium into nerve and muscle cells. With the gate plugged, the cells cannot fire signals. The paper says even very low concentrations cause paralysis and death. The National Geographic post adds that there is no antidote.

The toxin sits in the skin and other tissues. The paper says these salamanders neither store TTX in specific organs nor have a way to detoxify it. Where it comes from is unresolved. Some evidence suggests that bacteria produce the TTX found in salamanders, while other evidence suggests salamanders may make it themselves. Frogs have their own toxin story: the golden poison frog article explains where that frog’s poison comes from.

The newt also has a warning display. The Animal Diversity Web describes the unken reflex: when threatened, the newt bends its head back and curls its tail to show its bright belly. The toxin is not equal everywhere. The same source says toxicity varies by region, and the National Geographic post says that as newts grow more toxic, both their poison and the snakes’ resistance are magnified by a thousand times, across the 28 locations where newt toxicity was measured. The Animal Diversity Web says the toxin is dangerous only if swallowed. That is a reason to leave every newt alone, not a reason to pick one up.

How a toxic newt avoids poisoning itself

A newt full of a nerve toxin needs nerves that ignore it. Hanifin and Gilly report that the newt’s skeletal muscle sodium channel was barely affected by a high dose of TTX. They estimate that the channel is about 30,000 times more resistant to TTX than the matching channel of TTX-sensitive vertebrates, and roughly ten times more resistant than the channels of garter snakes or puffer fish. That is one paper, and we did not find a second source for the figure.

In plain terms, the lock on the newt’s nerves and muscles has been reshaped so the toxin key barely fits.

The arms race with garter snakes

The Animal Diversity Web says common garter snakes are the only known predator of the rough-skinned newt, and that they appear to be immune. Garter snakes are not a single case, though. A 2005 paper in the Journal of Chemical Ecology reports that another species, the aquatic garter snake Thamnophis couchii, has evolved elevated resistance in at least one area where it overlaps a related newt, Taricha torosa. Immunity turns out to be a matter of degree. Michael Hague and colleagues, in a 2018 paper in Evolution Letters, report that garter snakes in the west resist TTX through changes to their own muscle sodium channel. One version of the channel gave a 260-fold increase in resistance. The prey in this system are Pacific newts of the genus Taricha, the group that includes the rough-skinned newt.

Resistance has a price. In the California snakes studied, those with two copies of the most resistant channel crawled more slowly than snakes with the ancestral channel. The Pacific Northwest lineage showed no significant effect. The authors found resistant versions at high frequency in hotspots with toxic newts and rare in nearby coldspots with nontoxic newts, and suggest that resistance pays off where newts are toxic but costs too much where they are not. They note that the link between channel function and crawl speed was not directly tested in muscle tissue.

Biologists call this kind of back-and-forth the Red Queen effect, after a character in Lewis Carroll’s Through the Looking-Glass who has to run to stay in place. The National Geographic post on the Hanifin study, which measured newts at 28 locations, reports that poison and resistance were both magnified about a thousandfold across populations. It says that in every case the snakes were ahead, and that in a third of locations even the least resistant snakes could eat the most toxic newts. Hanifin speculated that if the cost of resistance is high enough, snakes could lose it and the race could resume. For the snake’s side, see the common garter snake article.

What this looks like in practice

Common mistakes and myths about toxic newts

Myth: the newt is dangerous to everyone. The Animal Diversity Web says the toxin is dangerous only if swallowed, and snakes with resistant channels eat newts without harm. That is not a license to handle one.

Mix-up: the orange belly is just decoration. The unken reflex shows it as a warning, as the Animal Diversity Web describes it.

Myth: every garter snake is immune and every newt is equally toxic. Both vary by place, which is the whole point of the arms race.

Mix-up: the toxin is a weapon the newt built for snakes. Our sources do not say why the toxin evolved, and they say its origin, bacteria or the newt itself, is unresolved.

Conservation status

The rough-skinned newt is listed as Least Concern on the IUCN Red List of Threatened Species. That is the category as distributed by GBIF, the Global Biodiversity Information Facility, and we checked it on November 9, 2026. Least Concern means the species was evaluated and does not meet the criteria for a threatened or near-threatened category.

Least Concern is not the same as no problems. The Animal Diversity Web says the species has no special status under U.S. federal listings or CITES, and notes that, as with many amphibians, it could face threats if development destroys its habitat. None of the sources we read reports a population decline, and none states a confirmed population trend.

Categories are reviewed and can change, and the copy GBIF distributes can trail the IUCN website by some months, which is why we print the date we checked. GBIF’s copy does not give the year of the IUCN assessment, so we do not state one.