Crocs and gators hang around with their mouths open as a way to avoid overheating. Keeping cool may be the primary purpose but for some species there's a secondary gain from the behavior. read more
They are cold -blooded and so their body temperature varies with that of the environment. Extra Info : Crocodiles have strong muscles to close it's jaws but the muscles required to open them are very weak. That is why a flimsy adhesive tape is enough to keep it's mouth shut, while transporting the croc elsewhere. read more
They do not have sweat glands. If a Crocodile gets too warm, it can only reduce it's temperature in three ways: get in the shade; get in the water; or sit quietly with its mouth wide open. The body heat therefore is lost through the soft, moist skin of the mouth and tongue. read more
Crocodiles open their mouths for 2 reasons: to cool off and to let spur-winged plovers get rid of parasites. the cooling is possible because the open mouth has more volume (surface area) for heat to escape. read more