Crocks, Gators, and Plovers

Crocs and gators keep 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. For crocodiles living in the range of the Egyptian plover, or 'crocodile bird', sitting around with their mouth open means they get free teeth cleaning from the small birds. The plover acts as both a dental hygienist and a warning system for danger.

PawNation writes, "The plover comes along and, using its sharp little beak like a toothpick, removes the bits of meat from between the crocodile's teeth. This feeds the plover and removes parasites from the croc's mouth. The plover serves as a security alarm system for the crocodile. If, while in the croc's mouth, the plover senses danger from an oncoming animal, it screams and flies away. This behavior alerts the crocodile to the imminent danger, so it can slide into the water and out of harm's way."