Why Do Crocodiles Have Their Mouths Open All the Time?

Saltwater crocodile with mouth open

Australian Scenics / Getty Images

The crocodile pictured above shows off a familiar pose, basking in the sun with mouth agape. Do they do this to look intimidating? Are they hoping some animal will wander close enough for it to snap down and have a snack? The reason is actually a lot more practical than all this.

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. For crocodiles living in the range of the Egyptian plover, or "crocodile bird," sitting around with your mouth open means you might get a teeth cleaning from one of these small birds. The plover acts as a dental hygienist and a warning system for danger.

In this symbiotic relationship, the (very brave!) plover visits the gaping maw and uses its sharp beak to remove bits of meat from between the crocodile's teeth. The plover gets a relatively easy meal; the crocodile gets its teeth cleaned.

Meanwhile, if the crocodile is relaxing while being groomed, the plover can act as an alarm as well. If the plover senses danger, it will make an alarm call and fly away. This alerts the croc to the potential presence of imminent danger, shaking it from its relaxed state and into action.

We love unusual relationships, especially when they involve the most fearsome and most delicate of friends.