© Taran Grant/AMNH

Kokoe Poison Frog (also Green-banded Poison Frog): Phyllobates aurotaenia

They don't sting or bite, but some frogs nevertheless can fend off the most ferocious foes. Their secret? Poison secreted from their skin. This chemical coating shields a frog from being eaten by predators. One tiny drop of toxin is all it takes to paralyze and in some cases kill a foe—including a person. Not all frog toxins are deadly, but even the weaker chemicals can cause numbness. Many also have a bitter taste that repels predators.

The various species of poisonous frogs come by their harmful chemicals in different ways. Most get their poisons from their food—chiefly ants and other arthropods—and some species can chemically alter the substances they ingest, turning mild toxins into more potent ones as yet unknown elsewhere in nature. But some species produce their own toxins, while still others use both of these techniques. Toxic frogs are immune to their own poison.

Foe or Faux?

Not all flashy frogs are poisonous. Scientists suspect a few nontoxic species evolved color schemes that mimic coexisting poisonous species. More study is needed to determine whether or not this line of defense really works.