What the heck is an unkel reflex?

Answer 1

Did you mean "unken" reflex? If so, it’s a natural reflex of several species of frogs, toads, salamanders and newts. They do it when bothered or threatened — usually by a predator, a creature wanting to eat them. They'll flip over and arch their backs, etc. It's a sign that means "don't eat me...I'm bad for you."