They're evolving...

This is clearly the first stage of an evolutionary leap that will ultimately lead to horrible, deadly creatures, of the sort previously confined to the fever-dreams of Japanese videogame designers: Exploding toads.

It has been speculated that [the swamp dragons'] habit of exploding violently when angry, excited, frightened or merely plain bored is a developed survival trait to discourage predators. Eat dragons, it proclaims, and you'll have a case of indigestion to which the term "blast radius" will be appropriate.
(Terry Pratchett, Men at Arms).