Baby Crocs Cry Inside Eggs

[Snowden]

Baby Crocs Cry Inside Eggs

By Jeanna Bryner, Senior Writer
posted: 23 June 2008 12:00 pm ET


Nile crocodiles are among the fiercest predators in southern Africa, yet their population has shrunk due to habitat loss and hunting. In another study, researcher Alison Leslie of the University of Stellenbosch found that climate change will also cause crocodile numbers to plunge. Credit: Oscar Baldomero.

The sounds "umph, umph, umph" might not resonate with you, but for baby crocodiles still in their shells, they are telling mom, "Let us out!"

Biologists have known that shortly before hatching, crocodiles make noises within their eggs. A new study, which involved playbacks of the pre-hatching calls, reveals these calls from the egg tell siblings it's time to hatch and tell moms it's time to uncover the nest.

Researchers Amélie Vergne and Nicolas Mathevon of the Jean Monnet University in France monitored Nile crocodile (Crocodylus niloticus) eggs that were due to hatch within 10 days. The eggs were placed into one of three groups, for which the researchers either played recordings of pre-hatching calls, recordings of noise (other than the calls), or no sound.

The group of eggs that got a dose of real croc calls responded and moved, as the about finger-sized babies jostled about, more often than the "noise" eggs. The eggs incubated in silence showed no movement.

All four of the individuals that successfully hatched in the croc-call group did so during or within 10 minutes of the playbacks. The pre-hatchlings in the noise group broke through their shells no less than five hours after the last playback.

After the eggs hatched, the moms-to-be stuck around to continue their nest guarding. The researchers found the female crocodiles responded to pre-hatching playbacks coming from loudspeakers hidden underground near the now-empty nests.

The female adults more often turned their heads or moved after egg sounds than after noise, and eight of the 10 mothers began digging in response to pre-hatching calls. (The nests are covered with soil during the months-long incubation.)

The Nile crocodile, Africa's largest croc can grow to about 20 feet (six meters) long and weigh up to 1,650 pounds (730 kg). Due to lethal human run-ins, the Nile crocodile has been labeled a vicious man-eater, but when it comes to parenting, these predators are nature's nurturers. Unlike many reptiles whose parenting responsibilities end once the mother lays her eggs, Nile croc moms vigilantly watch over their underground nests for about three months and even continue mothering for a period after the eggs hatch.

And so the researchers say the little grunts from inside the egg are likely critical to the early survival of the young crocodiles. The baby calls could attract attention from predators, the researchers say, making it important for all eggs to hatch at once so they receive care and protection from parents.

Some birds also vocalize to mom while inside their eggs, the researchers say. And so they speculate such acoustic communication at an early stage of development may be a shared behavioral feature of past and present archosaurs, a large group of animals that includes today's birds and crocodiles along with the now-extinct dinosaurs, pterosaurs and early croc relatives.

The study, detailed in the June 23 issue of Current Biology, was funded by the French Ministry of Research and the University Institute of France.



Baby Crocs Cry Inside Eggs | LiveScience

[Woodmonkey]

Interesting.

[Snowden]

Baby crocodiles chat to each other inside their eggs 'to synchronise hatching'


By Daily Mail Reporter
Last updated at 3:08 PM on 24th June 2008

Baby crocodiles start chatting to one another and to their mothers just before they hatch, researchers say.

The little reptiles make an 'umph! umph! umph!' noise and scientists believe they are signalling they are ready to be born.

"Crocodile mothers react strongly to playback of pre-hatching calls, most of them by digging the sand," Amelie Vergne and Nicolas Mathevon wrote in the journal Current Biology.

Crocodiles signal to each other just before they hatch

The researchers tested 10 crocodiles and their eggs, recording the sounds the babies made and then playing these, as well as random sounds, to the mothers.

The sounds seemed to spur siblings to start breaking out of their eggs, Vergne and Mathevon wrote.

"In the zoo where we did the experiments, eggs are removed within a few days after laying. In spite of this, females continue to guard the nest."

Eight of the mother crocodiles who were played recordings of the correct "umph" calls tried to dig up their clutches, while mothers who heard random sounds did not.

Mathevon said many baby reptiles are eaten right after birth, so it may be important for them all to hatch together and for the mother to be there when they do.

"In this sense, it is important for all embryos in the nest to be ready for hatching at the same time so that they all receive adult care and protection," he said.


Baby crocodiles chat to each other inside their eggs 'to synchronise hatching' | Mail Online