Mon Repos trial aims to boost turtle hatchling survival rates, combat heatwaves with 'artificial rain' – via Herp Digest

ABC Wide Bay By Nicole Hegarty

Sun 30 Dec 2018,

They are more commonly associated with parks and lawns, but sprinklers are now also lining a beach in south-east Queensland in a world-first trial to keep turtle nests cool and reduce heat-related deaths of the animals.

Rather than keeping grass green and lush, the "artificial rain" created by sprinklers at the renowned turtle rookery Mon Repos, near Bundaberg, has the job of lowering the sand temperature.

Mon Repos is the most important breeding site in the South Pacific for the endangered loggerhead turtle, and has the largest concentration of nesting marine turtles on eastern Australia's mainland.

Every year, from November to March, marine turtles nest and hatch on Mon Repos' beaches.

But in the past two seasons, heatwaves have elevated sand temperatures above 29 degrees Celsius — the ideal temperature for baby turtles to hatch from eggs buried in the sand.

Hotter sand, fewer turtles, more females

Dr Col Limpus, chief scientist with the Queensland Department of Environment and Science's threatened species unit, said the hotter sand had halved the rate of turtle eggs hatching.

"The last two summers we've had heatwaves and with the heatwaves, elevated sand temperatures causing the death of eggs and hatchlings," Dr Limpus said.

"Sand temperatures at the nest depth ... are getting above 32 degrees and that's getting into the level where we start to have failure of hatchlings.

"Not necessarily just [at] this beach, but [at] other beaches … instead of getting 80 per cent hatchling production we're looking at about 40 per cent, so they can be quite significant changes.

"The sand temperatures we're measuring these days are much higher than the temperatures we had when we started this work 50 years ago."

Hotter sand also has a secondary effect: the hatchlings are more likely to be female.

"The temperature of the nest also determines the sex of the hatchlings, and when you get hot nests, all you're going to get is females," Dr Limpus said.

"We run the risk of not getting enough male hatchlings. We want to bring temperatures down, so that we get a mix of male and female hatchlings.”

Artificial rain

A series of five sprinklers has been set up along the beach to create different amounts of "artificial rain" each night throughout the nesting season, Dr Limpus said.

"The control [sprinkler] station doesn't have any artificial rain.

"Then we have four sprinkler systems giving us artificial rain: one giving one hour of rain a night, the second one giving two hours of rain, the third one three hours of rain, the fourth one four hours of rain.”

By measuring the sprinkler water and how hot the sand is underneath, researchers are testing whether they can control the temperature of the sand.

"Hopefully we're going to come up with an equation which would tell us how much rain [would] bring temperatures down to any particular level," Dr Limpus said.

"Once we have that, we'll be able to provide advice to the park management so that in the future, if they wanted to be cooling beaches in the event of a heatwave, they'll have a recipe for how to go about it.”

The sprinklers could be another option in addition to shade cloths, which have been trialled in the past.

Battle for survival

The odds of survival are already stacked against the baby turtles.

It is thought only one in 1,000 of the hatchlings survive to maturity. For loggerheads, that is 30 years of age.

Hotter temperatures mean fewer baby turtles even reach the stage of hatching from their eggs and with more heatwaves forecast, researchers say time is of the essence.

"The Bureau of Meteorology is predicting another heatwave this summer so we're trying to look forward to find solutions that we could use in the future … to cool the sand in the event of excessive heatwaves," Dr Limpus said.

"The predictions are that it's going to get hotter in decades to come, so now is the time to look for options, not in the future when we have a major problem.”

If the trial is successful, sprinklers will be installed at other turtle nesting sites in Queensland.

Future generations

Turtles have helped put the Bundaberg region on the map.

Thousands of visitors make the night-time journey to Mon Repos each season to see the animals come to shore to lay their eggs, and in the following months, to witness the hatchlings make their way down the sand to the sea.

Bundaberg Tourism Board chairman Ross Peddlesden said the tourism industry supported any measure that would help preserve the turtle population for future generations.

"To be able to see conservation in action, to be able to see these marvelous animals breeding and hatching, all of those things are important," he said.

It is a sentiment shared by local Carmel Coney. 

"It's the first I've heard of it [the trial] but it sounds good," Ms Coney said.

"It [the rookery] is very important. I want it to be here for my grandson. I'm looking forward to seeing the results of the trial.”