There are more than 3,000 species of snakes on the planet and they’re found everywhere except in Antarctica, Iceland, Ireland, Greenland, and New Zealand. About 600 species are venomous, and only about 200—seven percent—are able to kill or significantly wound a human.

Nonvenomous snakes, which range from harmless garter snakes to the not-so-harmless python, dispatch their victims by swallowing them alive or constricting them to death. Whether they kill by striking with venom or squeezing, nearly all snakes eat their food whole, in sometimes astoundingly large portions.

Almost all snakes are covered in scales and as reptiles, they’re cold blooded and must regulate their body temperature externally. Scales serve several purposes: They trap moisture in arid climates.