Crocodilians' hearts have four chambers like mammals and birds, but there is a pore between the left and right ventricles which allows some mixing. Opening their mouths can also cool them off, since the large exposed wet surface allows much evaporation. Tropical species may avoid the hot sun by remaining under water or mud during the day. Alligators, which live in temperate regions, may remain completely submerged except for their nostrils when the air is very cold in the winter. After feeding, crocodilians tend to seek more heat, as it speeds digestion.
Crocodilians continue to grow their entire lives, even after sexual maturity has been reached.
Crocodilians' teeth are mostly identical, thick-walled cones embedded in the outside of the jaw. Rear teeth are more cylindrical and blunter than front teeth. The teeth are not cemented into the jaw but simply attached to the outside, and can be broken off. Crocodilians do not have lips and their mouths leak when closed. Their stomachs are the most acidic recorded for any vertibrate, allowing them to digest even the bones and shells of prey animals.