Scientists have discovered that baby crocodiles talk to each other from inside their eggs in order to synchronise hatching.
Writing in Current Biology, Jean Monnet University researchers Amelie Vergne and Nicholas Mathevon recorded the sounds made by a clutch crocodile eggs in the time leading up to hatching. They then played these sounds back to another group of eggs that were due to hatch within the next ten days. Surprisingly, most the eggs answered back, and many of them also moved around! But most importantly, all of them hatched out within ten minutes of hearing the sound.
As a control the team played random noise to another group of eggs, and left a third clutch in silence. Neither of these two groups showed any calling or hatching response. To find out why the crocodile hatchlings might be showing this behaviour the team also played the pre-hatching sounds, and some random noise, to nesting adult crocs in a zoo.
The adults responded by digging, moving or turning their heads to the egg-sounds, but not to the other noises. This, the researchers think, is a survival mechanism on the part of the hatchlings to time their emergence when adults are likely to be nearby to protect them from predators.
The authors point out that birds are also known to make noises from the egg that encourage parental care, and as birds are closely related to dinosaurs - birds and crocodiles may have inherited this behaviour from a common evolutionary ancestor!