California Newt, Taricha torosa

The unken reflex is a passive defense posture adopted by some toads, frogs and salamanders. When
threatened by predators, they twist their bodies or arch their backs to expose brightly-colored 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, the
unken reflex is sometimes accompanied by toxic secretions from the skin. This is the case with the
Rough-skinned Newt, which releases poisonous tetrodotoxin while engaging in the unkenreflex.

This behavior is named after a toad (German: Unke, plural: Unken) which exhibits this reflex.
The same behavior may be observed in other amphibians that do not have any warning colors.