Life Science Environment Implant turns ‘toxic Trojan’ bilbies into feral cat killers

Implant turns ‘toxic Trojan’ bilbies into feral cat killers

Bilbies in a South Australian reserve have been implanted with a poison which kills predators.
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In a ring-fenced reserve in the heart of South Australia, 30 innocent-looking bilbies have been turned into toxic Trojans.

Should a feral cat ever make a meal of them, it will be the cat’s last supper.

The bilbies are part of a groundbreaking trial of an ingenious new implant that sits just beneath their skin.

It is full of poison but thanks to a carefully-engineered coating, and the bilbies’ natural resistance to the toxin, it poses no threat to them.

When feral predators eat an implanted bilby, the predator dies too because the coating rapidly dissolves in stomach acid.

Kyle Brewer, from the University of South Australia, developed the coating for the implant, using polymer chemistry principles.

It took about a year and half to land on a polymer that is stable in the relatively neutral PH environment of a bilby’s body but quickly dissolves once it hits the acidic environment of a feral cat’s stomach.

Implants covered in the coating are now inside 30 bilbies that live on the fenced Arid Recovery Reserve in South Australia.

“It’s a protective buffer that aims to take out the feral invader in one stroke and that protects the rest of the native animal population,” Mr Brewer says.

The trial at the reserve has been going for about a year but has coincided with the inland mouse plague.

As a result, feral cat invaders have had plenty of mice to eat and have not taken any of the implanted bilbies, says Dr Katherine Moesby, who co-founded the reserve and helped develop the implant concept.

She says that’s “great for the bilbies, but not so great for the field trial”, which is trying to show that the solution works as it should in a natural setting.

The test will come when the mice vanish, and the feral cats start looking for something else to eat.

In the meantime, Mr Brewer is pressing on with efforts to extend the stability of implants so they cover the entire life of a bilby, which is about three to five years in the wild.

Dr Moesby says there’s no risk to the bilbies, even if the implants become unstable inside their bodies, because the animals have a natural tolerance to 1080 poison.

“It’s a synthetic poison that mimics a natural compound that’s found in a lot of native plants, particularly in South Australia and Western Australia,” she says.

“It’s what is used to poison foxes and even wild dogs. But most native animals that have co-evolved with that plant have high levels of tolerance to it.

“Even if we implanted the bilbies with three or four and they ruptured, they’d still be fine.”

Feral cats are one of the primary threats to native species in Australia, and have already caused the extinction of many ground-dwelling birds and small and medium-sized mammals.

Mr Brewer’s project is a collaborative effort that has also involved researchers from local ecology groups, including Dr Moesby’s ecological consultancy company Ecological Horizons, Peacock Biosciences, and the University of Adelaide.


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