Baby crocodiles call out when ready to hatch

Baby crocodiles call from their eggs to tell others in the nest when it is time to hatch, scientists have discovered. The calls, described by one researcher as an "umph, umph" sound, are thought to be critical to the survival of the animals. By calling and hatching together, baby Nile crocodiles increase the chances that a parent will remain at the nest and be able to protect them from predators in their first hours of life, scientists believe.
Writing in the journal Current Biology, Amélie Vergne and Nicolas Mathevon, at Jean Monnet University in Saint Etienne, France, describe how they divided crocodile eggs which were due to hatch within 10 days into three groups. One was played recordings of the pre-hatch calls made by baby crocodiles, a second was played random noises and a third left in silence. The researchers found that eggs played the pre-hatching calls often answered back, with many of them wobbling a little.
After 10 minutes, all of them had hatched.
Of the eggs in the other groups, only one egg that was played random noises hatched shortly afterwards, with the rest not emerging until at least five hours later.
With audio of the pre-hatch baby crocodile calls.