If you listen to the egg of a crocodile, you can tell when it’s going to hatch by the small squeaks coming out of it. The squeaks come from the unborn babies and sound like “umph! umph! umph!”. These calls are common to all crocodilians and while zoologists have always suspected that they serve a specific purpose, until now, no one had ever tested this theory with an experiment.

Amelie Vergne and Nicoals Mathevon at the Universite Jean Monnet are the first to do so and they show that the youngsters call to tell their siblings that it’s time to hatch. And given that Nile crocodiles bury their eggs in sand, the calls also tell the mother that it’s time to