Hot temperatures are changing the gender of lizards, study finds

Climate change could wipe out female lizards entirely, experts have warned

A 'Bearded Dragon' reptile is seen during the opening of the event 'Getting in touch with nature' in the new educational area at the Bioparco on October 12, 2013 in Rome, Italy (Giorgio Cosulich/Getty Images)

As the world warms, Australia’s bearded dragon lizards are changing gender and female chromosomes could disappear entirely, researchers have found.

For some reptiles, gender isn’t determined by sex chromosomes but how warm they are while they’re incubating — though not, until now, the lizards. But that seems to be changing, with hotter temperatures changing lizards at a biological level — and the newly-female lizards might even make better mothers than those with the female chromosomes.

Before the changes, lizards either had a W chromosome or they didn’t — if they did, they would be a genetic female, and if they only had Z, they’d be male. But a team of researchers from the University of Canberra have caught bearded dragons in the wild that have the male chromosomes, but seem to have outwardly female characteristics because of the increasing heat.

The study is the first to report reptile sex reversal in the wild. Researchers have shown before in lab settings that warm temperatures can change animal’s gender.

The researchers caught 131 of the lizards, and only 11 of them showed the new characteristics, reports Phys.org. Clare Holleley, the lead author of the study, told the site that she was aware the sample size was small and that the team would be looking to expand their research.

The researchers found that the lizards that had female characteristics but male chromosomes could even make better mothers, since they laid more eggs.

One of the authors of the study warned that if global warming continues, the amount of sex reversal could increase. That could lead to the W chromosome disappearing entirely and lead to the lizards determining their sex through temperature, like other reptiles.

Eventually, the heat could have the same effects on other animals. "It certainly can happen to other species, but it's not going to happen to humans, more than likely," Frederic Janzen of Iowa State University told Phys.org.

The team report their findings in a study published in Nature, called ‘Sex reversal triggers the rapid transition from genetic to temperature-dependent sex’.