Most Poisonous Animals: Dart Frogs, Pufferfish and More

Poisonous vs venomous: what is the difference?

A poisonous animal carries toxins in its skin, flesh or organs, and they work only when a predator bites, swallows or handles it. A venomous animal injects its toxins actively through fangs, stingers or spines. A golden poison frog is poisonous; a rattlesnake is venomous. Our guide Is a snake venomous or poisonous? explains the difference in more detail.

Poisonous animals often advertise their danger with bright colors, a strategy called aposematism, so that predators learn to leave them alone. For animals that inject their toxins, see our list of the most venomous animals.

1. Golden poison frog: enough toxin for 10–20 people

The golden poison frog (Phyllobates terribilis) lives only in the rainforests of Colombia’s Pacific coast. At up to about 6 cm (2.4 in) long, it is the largest of the poison dart frogs, and it comes in yellow, orange and mint-green forms. Its skin is loaded with batrachotoxin, a nerve poison that forces sodium channels in nerve and muscle cells to stay open, causing paralysis and heart failure.

A wild frog is estimated to carry about 1 mg of toxin, enough to kill roughly 10 to 20 people. Emberá hunters in Colombia traditionally wiped the tips of their blowgun darts across the frog’s back. The species is listed as Endangered by the IUCN because its small range is threatened by deforestation, mining and farming.

The frog does not make the poison from scratch. Golden poison frogs raised in captivity on ordinary insects are not toxic, and scientists suspect the batrachotoxin comes from small beetles in the wild diet.

2. Hooded pitohui: the poisonous bird

Birds were long thought to be harmless to touch, until 1990, when scientists preparing hooded pitohui (Pitohui dichrous) specimens in New Guinea noticed numbness and burning on their hands. Tests published in 1992 showed that the bird’s skin and feathers contain homobatrachotoxin, a relative of the frog’s poison, with the highest levels in the feathers of the breast and belly.

The pitohui probably gets its toxin from melyrid beetles of the genus Choresine, which contain the same compounds and have been found in the birds’ stomachs. Its toxin levels are far lower than a golden poison frog’s, but they are enough to make it unpleasant to eat and to discourage feather lice. Local people in New Guinea had long known that the bird tastes bad. Another New Guinea bird, the blue-capped ifrit, is toxic in the same way.

3. Pufferfish: tetrodotoxin in the liver and ovaries

Many pufferfish (family Tetraodontidae) contain tetrodotoxin (TTX), one of the strongest nerve poisons known. It is concentrated in the liver and ovaries, with smaller amounts in the skin and gut. TTX blocks the signals that nerves send to muscles, so poisoning can cause numbness, paralysis and breathing failure.

The toxin is thought to be produced by bacteria and built up through the food chain. Tiger puffers farmed in Japan on a controlled diet are essentially non-toxic. In Japan, Korea and China, pufferfish is eaten as a delicacy (fugu in Japanese), but only specially trained and licensed chefs may prepare it, and most poisonings come from fish cleaned at home. Read more in Are pufferfish poisonous?

4. Rough-skinned newt: a predator arms race

The rough-skinned newt (Taricha granulosa) of the Pacific coast of North America, from southeastern Alaska to California, makes the same tetrodotoxin as pufferfish. Some newts carry enough to kill several adult humans, and in 1979 a 29-year-old man in Oregon died after swallowing one on a dare. The newt is harmless to look at; the danger comes from eating it.

Only one predator regularly eats it: the common garter snake. Over thousands of generations, newts in some areas have become more toxic and snakes there more resistant, a classic evolutionary arms race described in How do garter snakes eat toxic newts?

5. Cane toad: an invasive toxic giant

The cane toad (Rhinella marina) is native from southern Texas to the Amazon. Large parotoid glands behind its eyes, plus smaller glands across its back, ooze a milky poison called bufotoxin when the toad is threatened. In August 1935, 102 toads brought from Hawaii were released in Queensland, Australia, to control beetles in sugarcane fields.

The toads failed at that job but spread across northern Australia. Native predators that had never met toads, such as northern quolls, large monitor lizards and freshwater crocodiles, died after eating them, and quolls disappeared from parts of Kakadu National Park. Cane toads are also established in Florida, Hawaii and many Pacific and Caribbean islands.

6. Fire salamander: Europe’s poisonous amphibian

The fire salamander (Salamandra salamandra), black with bright yellow or orange markings, lives in damp forests across much of Europe. Glands in its skin release alkaloid toxins, chiefly samandarin, which cause muscle convulsions and high blood pressure in predators. Unlike poison frogs, the salamander makes these toxins itself rather than taking them from its food. Since 2023, the IUCN has listed it as Vulnerable, mainly because an introduced fungal disease, Batrachochytrium salamandrivorans, has wiped out populations in parts of western Europe.

7. Monarch butterfly: poisonous from its food plant

Monarch caterpillars (Danaus plexippus) feed on milkweed and store its bitter heart toxins, called cardenolides, in their bodies, keeping them into adulthood. In classic experiments in the 1960s, blue jays that ate a toxic monarch vomited soon afterward and then refused to touch monarchs again. The bright orange and black wings act as a warning. Monarchs are harmless for people to touch or watch. Learn more about this famous migrant on our monarch butterfly page.

8. Yellow boxfish: toxic slime under stress

The yellow boxfish (Ostracion cubicus) of Indo-Pacific reefs lives inside a rigid, box-shaped armor of bony plates. Juveniles are bright yellow with black spots, a warning to predators. When stressed, the fish releases a toxin called ostracitoxin in its skin mucus, which destroys the red blood cells of fish and can kill other fish nearby in enclosed water.

9. Surprising cases: snakes and bears

A few animals are both venomous and poisonous. The Asian tiger keelback snake (Rhabdophis tigrinus) has a venomous bite, and it also stores toad toxins from its prey in special glands on its neck, which it uses to defend itself.

Even large predators can be dangerous to eat. Polar bear liver contains so much vitamin A, built up from its diet of seals, that Arctic peoples and early polar explorers learned it is too toxic to eat.

Where do poisonous animals get their toxins?

There are three main routes. Some animals make their own toxins, as cane toads and fire salamanders do. Others take them from their diet, like poison dart frogs, pitohuis and monarch butterflies. A third group relies on bacteria: tetrodotoxin turns up in such unrelated animals as pufferfish, newts and the blue-ringed octopus, which suggests that microbes are the true chemists.

This is why many poisonous animals lose their toxicity in captivity, where their diet is different.

How to stay safe

Poisonous animals are only dangerous if you handle or eat them, so the simple rule is to look but not touch. Never eat wild amphibians, and eat pufferfish only from licensed restaurants. If someone has swallowed part of a toxic animal or becomes unwell after handling one, seek emergency medical help immediately: call 911 in the US, 112 in the EU or 999 in the UK.