Lizards of Oz take toll on turtle eggs

Goannas have overtaken foxes as the number one predator of the endangered loggerhead turtle at its second largest Queensland nesting beach.

A University of Queensland study has found that since feral red foxes were controlled in the 1980s, there has been an increase in the number goanna raids on loggerhead turtle nests at Wreck Rock beach, south of Agnes Waters.

UQ School of Biological Sciences researchers PhD student Juan Lei and Dr David Booth observed - with the assistance of Turtle Care Queensland Inc volunteers and camera traps - that the predators disturb up to 400 nests at the beach in one year. 

“We discovered that only large male yellow-spotted goannas dug open sea turtle nests, but once the nest was opened other lizards, such as lace monitors and smaller yellow-spotted goannas, raided them,” Dr Booth said.

“We had expected most nests would be discovered within one or two days of being constructed because of the visual and scent cues left behind by the female turtle.

“But what we found was the likelihood of a turtle nest being opened by a goanna wasn’t related to the nest age or even the presence of ghost crabs, which disturb nests by burrowing and potentially releasing those smells that attract a goanna’s attention.

“So we still don’t know the mechanism by which goannas discover and attack sea turtle nests that are several weeks into the incubation period.”

Dr Booth said studying the relationships between predators and prey, and the interactions between different predators that hunt the same prey, were important in ecological research.

“One predator species may provide the cue signalling the location of prey to the other predator species, particularly when food sources become sparse,” he said.

The study, supported by a Nest to Oceans Turtle Protection Program grant, is published in Austral Ecology (doi:10.1111/aec.12568).

Media: Dr David Booth, d.booth@uq.edu.au +61 7 336 52138 or 0403 858 940.