7% of Australia's Reptiles Face Extinction

Populations of the grassland earless dragon (Tympanocryptis pinguicolla) have been declining, mostly because of feral cats. John Wombey/CSIRO/WIkimedia Commons

The International Union for Conservation of Nature (IUCN) released its latest update to the Red List, a rundown of threatened species around the globe, and a look at one particular continent is eye-opening: Almost all of Australia's reptiles are on the list.

The Red List now includes 975 Australian reptiles, which is nearly every species on the continent. The majority of them are endemic to the continent. Seven percent of the species face extinction if action isn't taken.

"Understanding the threats to each of Australia's native reptile species will help us effectively work with the Australian government, local conservation groups and Aboriginal people to address them," Philip Bowles, IUCN SSC Snake and Lizard Red List Authority Coordinator, said in a statement.

Threats from invaders

Australia's reptile population has largely evolved in isolation, allowing for a diverse collection of species. In fact, Australia's reptile population represents almost 10 percent of the world's overall reptile fauna, according to the IUCN, making it a major hub of reptile species. Given their proliferation, it shouldn't be a surprise that reptiles, from lizards to pythons, play a large part in the country's ecosystems as well the culture of the indigenous people.

The dangers to the reptiles haven't come from within the borders of Australia — not exactly anyway. According to the IUCN, invasive species are the primary threat to over half of the threatened reptile species on the continent. The IUCN pointed to a January 2018 study, which determined that invasive feral cats alone are responsible for the deaths of 600 million reptiles a year.

The feral cat population in Australia varies wildly, but it's estimated to be between 2.1 and 6.3 million as of October 2017. The cats are present on practically the entire continent.

One species feral cats are particularly fond of is the grassland earless dragon (Tympanocryptis pinguicolla). This tiny dragon — it can grow to be about 16 centimeters — favors grassland areas, as its name suggests. In addition to the feral cats gobbling them up, habitat destruction and changes in wildfire patterns pose significant dangers to its survival. The species had adapted to semi-natural wildfires that have changed over the centuries thanks to different land management practices, according to the IUCN.

A collection of cane toads sit in a container
Cane toads were introduced to control species, not eliminate them entirely. Ian Hitchcock/Getty Images

Feral cats aren't the only invasive species causing problems for reptiles, however. Cane toads — which were introduced to Australia in 1935 to control beetle populations that destroyed lucrative sugar crops — have caused havoc with poisonous venom that can kill many native animals and their startlingly rapid evolution that allows them to hope in a straight line, covering more distance at a faster pace.

This is particularly bad for reptiles like Mitchell's Water Monitor (Varanus mitchelli), which dines on cane toads and then dies after doing so. The species is now considered critically endangered by the IUCN following a population decline of 97 percent in some areas.

Other animals aren't the only external threat, however. Climate change poses a serious danger to various reptiles, including the Bartle Frere cool-skink (Techmarscincus jigurru). This cold-adapted reptile favors the chilly climates of Mount Bartle Frere's summit. A temperature increase of 1 degree Celsius could result in a 50 percent loss in the lizard's population within 30 years since it won't have any place colder to move to. The species is already considered vulnerable.

"This Red List update highlights the vulnerability of Australia's lizards and snakes to invasive alien species, including the toxic cane toad and feral cats, often in combination with threats from habitat loss due to invasive weeds, development and fire."