The battle to stop goannas in Queensland eating loggerhead turtle eggs has been highlighted in the international conservation journal Oryx, published today.
Loggerheads are listed as critically endangered on the IUCN Red List but in recent years goannas have increasingly been digging up and eating eggs – hampering efforts to rebuild loggerhead numbers.
The large reptiles are a particular problem at Wreck Rock Beach which supports the second largest number of loggerhead turtles nesting on the eastern Australian mainland, with 400 nests per season.
Christine Madden Hof, Marine Species Project Manager for the World Wide Fund for Nature-Australia is lead author of the scientific paper which explains trialling aluminium mesh, placed over nests, to stop the goannas.
Long-term volunteers Nev and Bev McLachlan, from Turtle Care, are also named as authors and were crucial to the trial.
Fifty-seven nests were monitored – 33 covered with the mesh and 24 control nests with no protection – in the 2013-14 breeding season.
Goannas dug up eggs in only about 15% of covered nests compared to nearly 50% of control nests.
But when cyclone Dylan made landfall near Wreck Rock beach (January 2014) the nests lost to the combination of predators and beach erosion was more than 90%.
“The double whammy of storms and goannas was brutal. If the climate change forecasts of more severe storms impact Wreck Rock it makes it even more important to deter goannas,” said Ms Hof.
While the mesh devices provided some protection they are not a long-term solution at Wreck Rock Beach.
“The mesh devices were time consuming to construct and dig into position. With so many nests to protect along a 23km stretch of beach, and limited numbers of volunteers, they are not cost-effective,” said Ms Hof.
Instead, attention has now turned to one of Queensland’s worst introduced pests – the cane toad – as one possible answer to the goanna problem.
Toads release poison when attacked and Queensland goannas, with decades of exposure to toads, have learned to avoid them.
A few road-kill toads, that were placed on top of nests, appeared to deter goannas at Wreck Rock Beach
Dr David Booth, from Queensland University, along with Nev and Bev McLachlan are planning a trial this summer to properly test if cane toad smell works to keep goannas away from nests.
If so it could be a practical way to protect loggerhead turtle eggs and help rebuild the population.