Naked Mole Rat
(Heterocephalus glaber)

Found in the dry grasslands of East Africa, the Naked Mole Rat is one of the most biologically bizarre mammals alive. Unlike virtually every other mammal, it is ectothermic — meaning it cannot regulate its own body temperature internally and instead relies on its environment to stay warm, behaving more like a reptile than a mammal in this respect.

It also lacks certain pain-related neuropeptides, making it effectively immune to some forms of pain, and can survive in oxygen levels so low they would cause brain damage in humans by switching its cellular metabolism to run on fructose rather than glucose — a trick no other mammal is known to perform!