This suggests that communal egg-laying is much more common than previously thought, and it is now necessary to explore why it occurs in these species.'

'Building a nest can be hard work for reptiles,' Doody said. 'Some female lizards may spend days digging a hole deep enough to deposit eggs. During that time she is not doing other important things such as finding food.'

'She is also more vulnerable to predators. Females can avoid these costs by simply laying eggs in a nest that someone else has gone to the trouble to build. But sharing nests can also have a downside,' Doody said, according to an ANU release.

'When the eggs hatch, babies are immediately forced to compete with each other for resources. In addition, closely packed egg groups have an increased risk of disease transmission.'

The research was published in the September issue of the Quarterly Review of Biology.