How Do Baby Turtles Hatch Simultaneously?

A study of Australian river turtles may help to explain why turtle eggs tend to hatch at the same time. Researchers believe that the buildup of carbon-dioxide in the nest could be a signal to embryonic turtles to increase metabolic rates and coordinate hatching times. To test this theory, scientists separated a batch of eggs, keeping half at a low temperature and half at a high temperature for two-thirds of the incubation period. The eggs were then brought together for the final days. The result: the cooler eggs, which would typically take longer to hatch, caught up to the warmer eggs, and all hatched together.

"An egg is actually breathing. It’s sucking in oxygen and expiring carbon dioxide,” explained Ricky-John Spencer at the University of Western Sydney. “If you’ve got a lot of well-developed eggs in the nest, there would be more CO2."

Females are hot, males are cool:

• Coordinated hatching times enable turtles to leave the nest in a group -- giving the hatchlings a better chance of escaping from predators.
• Sea turtles lay up to 100 eggs in sand nests. The temperature of the sand actually helps determine the gender of the baby turtles. Cooler sand produces more males and warmer sand produces more females.
• Temperature-Dependent Sex Determination, or TSD, governs the genders of other reptiles, including alligators and crocodiles. Warming trends due to climate change may cause a higher ratio of females to males and could potentially affect genetic diversity.