Unkenreflex

Unkenreflex – interchangeably referred to as unken reflex (Unke is the German word for fire-bellied toads) – is a defensive posture adopted by several branches of the amphibian class – including salamanders, toads, and certain species of frogs.

[1] Implemented most often in the face of an imminent attack by a predator, unkenreflex is characterized by the subject’s contortion or arching of its body to reveal previously hidden bright colors of the ventral side, tail, or inner limb; the subject remains immobile while in unkenreflex.

[2] During the course of unkenreflex, the amphibian in question releases bufotoxins from its parotid glands, tenses its entire body, and swallows air to bloat itself in an attempt to look larger.

[2] Certain species of anurans, such as the adult male Rana macrocnemis, only half-complete unkenreflex (also called low-intensity, or partial unken reflex) by only twisting its body slightly and not revealing the entire underside coloring,[1] or by shielding their face with raised feet that have dramatic coloration, or by curling their tail and exposing the tail's underside.

[5][6] This behavior is named after the fire-bellied toad (German: Unke; combining form: Unken-) which exhibits this reflex.