Warmer beaches influence sex ratios of loggerhead hatchlings

Oct 22, 2013 by Geoff Vivian
Warmer beaches influence sex ratios of loggerhead hatchlings
"Western Australia hosts one of the largest loggerhead rookeries in the world but one of the least known in terms of its physiology and its nesting biology"—Dr Mitchell. Credit: Florida Fish & Wildlife

While Dirk Hartog Island is the southernmost rookery for loggerhead turtles (Caretta caretta), UWA and Murdoch University biologists say climate change may ultimately lead to the species nesting successfully on beaches further south.

As all marine turtles have temperature-dependent sex determination, UWA herpetologist Nicola Mitchell and her collaborators have been studying the effects of temperature on gestating from the island.

"My main motivation is trying to anticipate impacts of ," Dr Mitchell says.

"Our recent study contains the physiological work that was needed to inform our computer models of hatchling sex ratios."

She says warmer temperatures during the middle third of the egg incubation period result in a high proportion of female hatchlings.

A team led by her Master of Science student Lorian Woogar, collected loggerhead eggs from Gnaraloo Bay, near Carnarvon and studied them at the laboratory at UWA.

"It turned out that they don't have very different pivotal temperature to other loggerhead populations in the world," Dr Mitchell says.

"Western Australia hosts one of the largest loggerhead rookeries in the world but one of the least known in terms of its physiology and its nesting biology.

"Now we know that it has a typical pivotal temperature of 29 degrees; that's where you get equal balances of males and females.

"The other new thing we've done is to model how development rates vary with the temperature.

"We can predict when embryos slow down in development when they get too hot.

"We now can predict at any particular nest , how much development occurs each day.

"Using that information we can then say, 'okay the embryo reached 40 per cent of development on this date, and this is when its sex was determined' and then we can infer the clutch sex ratio from there."

Dr Mitchell says the collected eggs were kept chilled for transport to Perth.

"We incubate eggs at certain temperatures we've optimised as temperatures of interest," she says.

Females breed every four years, producing five clutches of eggs during breeding season.

While sea turtles usually return to their own hatching site to nest, they have been known to lay eggs at other locations.

When events such as cyclones take them too far from preferred nesting beaches they will lay eggs at a nearby convenient beach.

Dr Mitchell says this combination of circumstances may in time lead to the establishment of viable rookeries on beaches further south.

Explore further: Researchers predict painted turtles face extinction due to global warming

add to favorites email to friend print save as pdf

Related Stories

'Heat-proof' eggs help turtles cope with hot beaches

Sep 26, 2011

(PhysOrg.com) -- Sea turtles face an uncertain future as a warming climate threatens to reduce their reproductive viability. However, new research led by the University of Exeter and published this week in ...

Scientists warn of climate change risk to marine turtles

Feb 20, 2007

North American marine turtles are at risk if global warming occurs at predicted levels, according to scientists from the University of Exeter. An increase in temperatures of just one degree Celsius could completely eliminate ...

Nesting Gulf loggerheads face offshore risks

Jul 15, 2013

Threatened loggerhead sea turtles in the northern Gulf of Mexico can travel distances up to several hundred miles and visit offshore habitats between nesting events in a single season, taking them through waters impacted ...

Recommended for you

Invasive vines swallow up New York's natural areas

8 hours ago

(Phys.org) —When Antonio DiTommaso, a Cornell weed ecologist, first spotted pale swallow-wort in 2001, he was puzzled by it. Soon he noticed many Cornell old-field edges were overrun with the weedy vines. ...

Citizen scientists match research tool when counting sharks

23 hours ago

Shark data collected by citizen scientists may be as reliable as data collected using automated tools, according to results published April 23, 2014, in the open access journal PLOS ONE by Gabriel Vianna from The University of Wes ...

Researchers detail newly discovered deer migration

Apr 23, 2014

A team of researchers including University of Wyoming scientists has documented the longest migration of mule deer ever recorded, the latest development in an initiative to understand and conserve ungulate ...

How Australia got the hump with one million feral camels

Apr 23, 2014

A new study by a University of Exeter researcher has shed light on how an estimated one million-strong population of wild camels thriving in Australia's remote outback have become reviled as pests and culled ...

User comments : 0

More news stories

Genetic code of the deadly tsetse fly unraveled

Mining the genome of the disease-transmitting tsetse fly, researchers have revealed the genetic adaptions that allow it to have such unique biology and transmit disease to both humans and animals.

Ocean microbes display remarkable genetic diversity

The smallest, most abundant marine microbe, Prochlorococcus, is a photosynthetic bacteria species essential to the marine ecosystem. An estimated billion billion billion of the single-cell creatures live i ...

Study links California drought to global warming

While researchers have sometimes connected weather extremes to man-made global warming, usually it is not done in real time. Now a study is asserting a link between climate change and both the intensifying California drought ...

Autism Genome Project delivers genetic discovery

A new study from investigators with the Autism Genome Project, the world's largest research project on identifying genes associated with risk for autism, has found that the comprehensive use of copy number variant (CNV) genetic ...