These flying creatures have a spikey tail, pincers and flame breath. Only the latter is really much cause for concern.
Sometimes they carry surprisingly rare loot! Make sure you search them before their corpses plummet to earth.
Added by Sway - A tougher, unique Rambo-style chupacabra was recently added. Killing it gets you a new journal entry (killed a unique chupacabra). It is called a Chambocabra and uses an AK.