The unken reflex is a passive defense posture adopted by toads, frogs and salamanders. When threatened by predators, they twist their bodies, or arch their backs and limbs to expose brightly-colored aposematic

Aposematism

Aposematism , perhaps most commonly known in the context of warning colouration, describes a family of antipredator adaptations where a warning signal is associated with the unprofitability of a prey item to potential predators...

 skin. The normally-concealed red, yellow, white and black patterns on the underbelly, inner surfaces of the limbs or underside of the tail serve as a visual warning to predators. To reinforce the warning, unken reflex is sometimes accompanied by toxic and malodorous secretions from glands in the skin. This is the case with the Rough-skinned Newt

Rough-skinned Newt

The rough-skinned newt is a North American newt known for its strong poison.- Toxicity :Many newts produce toxins to avoid predation, but the toxins of the genus Taricha are particularly potent...

, who releases the toxin tetrodotoxin

Tetrodotoxin

Tetrodotoxin, also known as "tetrodox" and frequently abbreviated as TTX, sometimes colloquially referred to as "zombie powder" by those who practice Vodou, is a potent neurotoxin with no known antidote. There have been successful tests of a possible antidote in mice, but further tests must be...

 while engaging in the unken reflex.

This behaviour is named after the Fire-bellied toad

Fire-bellied toad

The Fire-bellied Toads is a group comprising eight species of small toads belonging to the genus Bombina...

 (German: Unke; plural: Unken) which exhibits this reflex. The same behaviour may be observed in other amphibians that do not have any warning colours.