Isolated western tiger snakes resort to inbreeding

Perth's the most isolated capital city in the world, and new WA research suggests some of its tiger snake populations are turning to inbreeding.
Zaya Altangerel
Zaya Altangerel
Senior Content Producer
Isolated western tiger snakes resort to inbreeding
Image credit: Damian Letoof

Australia is notorious for being home to some of the world’s deadliest animals. Drop bears, danger noodles, crocs, sharks, deceivingly beautiful stingers and even spiders that rain from the sky – we have it all.

And now, according to new research from Curtin University, the western tiger snake, which is venomous, has started to inbreed in some areas of Perth.

Video gif of Oprah Winfrey exclaiming 'What?!'
Image credit: GIPHY

While they haven’t started growing an extra head (yet), if you suffer from ophidiophobia, you may want to skip this story. (And you really don’t want to visit Carnac Island, off the coast of Freo.)

The great divide

Like many capital cities, Perth has a problem with urban sprawl. It increases the urban heat island effect and makes us more reliant on cars.

It also has a big impact on the ecosystem. Last year, Curtin University PhD candidate Damian Lettoof found tiger snake populations within Perth’s wetlands to be accumulating high levels of toxic heavy metals due to pollution.

To make matters worse, it turns out the age-old question that has divided the humans of Perth for decades – north or south of the river? – is taking its toll on tiger snakes as well.

“There’s large rivers that cut through the city, which has separated the tiger snake population into north and south,” says Damian.

And unlike Perth’s human population, tiger snakes cannot easily travel across the river to visit other ‘urban islands’. As a result, those living in smaller wetlands are more likely to inbreed.

Isolation limits mate choice

Before urbanisation, western tiger snakes are thought to have moved freely throughout the Swan Coastal Plain using seasonal wetlands.

But thanks to widespread development, they’re now restricted to a handful of isolated lakes and river edges.

Damian and his team sampled ventral (belly) scale clips from 150 western tiger snakes from six wetlands across the southern and northern suburbs.

They found that tiger snake populations at Loch McNess (also known as Yanchep Lake), Lake Joondalup and Herdsman Lake had much lower genetic diversity than those at Bibra Lake, Kogolup Lake in Beeliar and Black Swan Lake.

For the sake of comparison, they also tested nine tiger snakes living on Carnac Island, where the species is thought to have been introduced around 90 years ago.

Gene pool size matters

Genetic diversity often indicates the capacity of a species to adapt to changes in its environment.

“If you’ve got a population with a huge amount of diversity, you might have some individuals that can tolerate really cold weather, some individuals that can tolerate really hot weather or more parasites,” says Damian.

“So if one of those stressors increases and it knocks out half the population that aren’t suitable for it, you’ve still got the other half that have the capacity to exist. And they can start breeding their genes into the population so they can adapt and survive.”

So what does this mean for tiger snakes at Herdsman Lake and Carnac Island, which showed the highest ‘signal’ of inbreeding?

Video gif of Indiana Jones (played by Harrison Ford) saying:
Image credit: GIPHY

S-s-survival of the fittest

While inbreeding increases the risk of genetic disorders, Damian says it’s not causing physical deformities at this stage.

“It could be having an impact on some molecular level or something that we can’t easily measure physically,” says Damian.

That’s because, while Perth’s wetlands are isolated, they support enough tiger snakes to maintain genetic variation.

“The inbreeding genes are not really taking over, and there’s only a handful of individuals with them,” says Damian.

A sign of ecosystem health

Although western tiger snakes are not yet inbreeding to a significant level, it does not mean the species are completely safe.

Western tiger snakes have relatively long lives, with most living up to 10 years. As a result, changes in their population and its impact will take some years to become noticeable.

Still, if Perth continues to become a sprawling concrete jungle, Damian and his team predict that inbreeding among western tiger snakes will become more common.

“The best thing is connectivity,” says Damian.

“For wetlands that are already isolated, the best thing we can do is maintain or restore remnant vegetation and try to uphold the best habitat quality we can.”

“For new areas that are being developed that have wetlands, connectivity needs to be incorporated into the plan from the beginning.”

“We need more complex vegetation and habitats that can support snakes and other species.”

Western tiger snakes are a top predator after all.

“Their presence in a wetland indicates that there’s enough food and required habitat for them.”

So in the future, if researchers like Damian start to notice something going really wrong with the western tiger snake, it’s likely that the surrounding ecosystem is being affected as a whole.

And that’s a problem we definitely want to avoid.

Zaya Altangerel
About the author
Zaya Altangerel
Zaya is a writer with a question for everyone and everything, but she's especially interested in music, food and science.
View articles
Zaya is a writer with a question for everyone and everything, but she's especially interested in music, food and science.
View articles


We've got chemistry, let's take it to the next level!

Get the latest WA science news delivered to your inbox, every fortnight.


Creative Commons Logo

Republishing our content

We want our stories to be shared and seen by as many people as possible.

Therefore, unless it says otherwise, copyright on the stories on Particle belongs to Scitech and they are published under a Creative Commons Attribution-NoDerivatives 4.0 International License.

This allows you to republish our articles online or in print for free. You just need to credit us and link to us, and you can’t edit our material or sell it separately.

Using the ‘republish’ button on our website is the easiest way to meet our guidelines.


You cannot edit the article.

When republishing, you have to credit our authors, ideally in the byline. You have to credit Particle with a link back to the original publication on Particle.

If you’re republishing online, you must use our pageview counter, link to us and include links from our story. Our page view counter is a small pixel-ping (invisible to the eye) that allows us to know when our content is republished. It’s a condition of our guidelines that you include our counter. If you use the ‘republish’ then you’ll capture our page counter.

If you’re republishing in print, please email us to let us so we know about it (we get very proud to see our work republished) and you must include the Particle logo next to the credits. Download logo here.

If you wish to republish all our stories, please contact us directly to discuss this opportunity.


Most of the images used on Particle are copyright of the photographer who made them.

It is your responsibility to confirm that you’re licensed to republish images in our articles.


All Particle videos can be accessed through YouTube under the Standard YouTube Licence.

The Standard YouTube licence

  1. This licence is ‘All Rights Reserved’, granting provisions for YouTube to display the content, and YouTube’s visitors to stream the content. This means that the content may be streamed from YouTube but specifically forbids downloading, adaptation, and redistribution, except where otherwise licensed. When uploading your content to YouTube it will automatically use the Standard YouTube licence. You can check this by clicking on Advanced Settings and looking at the dropdown box ‘License and rights ownership’.
  2. When a user is uploading a video he has license options that he can choose from. The first option is “standard YouTube License” which means that you grant the broadcasting rights to YouTube. This essentially means that your video can only be accessed from YouTube for watching purpose and cannot be reproduced or distributed in any other form without your consent.


For more information about using our content, email us:

Copy this HTML into your CMS
Press Ctrl+C to copy