Turtles 'communicate' before they hatch so they emerge from their shells at the same time

As if by magic, Australian freshwater turtles have been found to ‘communicate’ with each other so that they hatch at the same time.

Researchers at the University of Western Sydney (UWS) made the discovery after eavesdropping on clutches of the critters.

They realised that somehow Murray River turtles picked up on cues from their siblings to synchronise their maturation and emerge from their shells equally developed and at exactly the same time – a feat that appears to be biologically impossible.

Eggs-traordinary: Murray River turtles somehow 'talk' to each other so they emerge from their shells at the same time

The power of synchronicity or coordinated activity in nature is not uncommon. Fish swim in schools as if they are of one mind. Coral spawn en-mass. Birds fly in perfect formation.



Often it's for protection and for the turtles, which have the Latin name of E. macquarii, this is probably true as well.

The results of this unique study are reported this week in the prestigious international journal, Proceedings of the Royal Society B, by Dr Ricky Spencer and colleagues in the UWS School of Natural Sciences.

‘Female turtles lay their eggs and then abandon the nest. Without the protection of adult turtles there is a distinct advantage for a coordinated departure from the nest for the young turtles,’ says Dr Spencer.

‘The mass escape from the nest may confuse predators, decrease the chances of individuals being eaten and the combined effort of digging out of the nest is undoubtedly easier than going it alone.’

While the benefits of synchronous hatching in the wild are clear it took clever science in the lab to uncover the mystery buried in the nest.

Animal magic: It's possible that other turtles, such as these black turtles in Guatemala, can also perform the feat

Dr Spencer, fellow UWS researcher Dr Julie Old and UWS PhD candidate Jessica McGlashan divided clutches of E. macquarii eggs and incubated some at 30C and some at 26C for seven days before reuniting them to complete their development at the same temperature in close proximity in the same 'nest'.

The embryos in the eggs which experienced a period of warmer temperature were - as expected - more developed compared to their 'cooler' siblings at the time they were reunited.

The team then used sophisticated instruments to measure the metabolic rates of the reunited eggs right through to hatching.

A non-intrusive method using infrared transmitters and sensors amplified the cardiovascular signal of an embryo within the egg by 20,000 times.

The respiration of the egg was measured by plotting the production of carbon dioxide in a special enclosed monitoring system.

‘It was assumed turtles had a very limited capacity to regulate metabolic processes independent of temperature. Increasing metabolic rates and boosting development rates without raising temperatures in the nest was really considered impossible,’ says Dr Spencer.

‘However, our study revealed in the presence of more developed E. macquarii embryos, under-developed embryos do accelerate their heart rates, their metabolic rates and as result their development accelerates to catch up to their siblings in the nest.

