Novel implant turns Australia’s threatened wildlife into a poisoned chalice for feral predators

As intelligent and notoriously cunning predators, feral cats have proven exceptionally difficult to manage in Australia. They threaten the survival of more than 100 native species and are responsible for the death of more than 815 million mammals each year – but a newly developed population management technique might curb this devastating loss.

In a novel approach to feral cat population control, researchers at the University of South Australia (UniSA) have found a way to turn prey species into poisoned chalices.

Using polymer chemistry principles, researchers at UniSA’s Applied Chemistry and Translational Biomaterials Group have created rice-sized implants, known as Population Protecting Implants (PPI), that are laced with a potent toxin derived from a natural poison in native plants.

The PPIs are then implanted directly under the skin of native mammals, such as bilbies, bettongs or quolls. Protected by an inert coating, they cause no harm to their mammalian hosts – but become deadly upon contact with the gastric juices of a predator’s stomach.

UniSA PhD student and 2021 recipient of an Australian Wildlife Society research grant, Kyle Brewer, says that PPIs could provide a solution to the historically beleaguered efforts to reintroduce native mammals outside fenced areas, where feral cat population control is most difficult.

“By injecting native species with the PPI before they are reintroduced to their natural environment, we’re providing a protective buffer that aims to take out the feral invader in one stroke,” says Brewer.

Cats in the wild are rarely predisposed to take baits, preferring to hunt and capture live prey. But by making the prey themselves the delivery mechanism, this technique cleverly sidesteps the natural ability of these predators to recognise and avoid a trap.

Together with other novel technologies – such as the Felixer device developed by the University of Adelaide’s Dr John Read – this new approach to feral cat control that targets natural cat behaviours could significantly boost the success of native species reintroduction programs. Although the toxin delivery pathway inevitably involves the loss of at least a portion of released individuals, the pay-off stands to be enormous – for every PPI-carrying individual lost to cats, approximately 700 other native animals will be spared the same fate.

Preliminary results should soon indicate the on-ground success rate of this technique. In a collaborative effort involving researchers from local ecology groups, Ecological Horizons and Peacock Biosciences, and the team at the University of Adelaide, a trial run has implanted PPIs in 30 bilbies and subsequently released them at Arid Recovery, a 123 square kilometre wildlife reserve near Roxby Downs, in South Australia’s north.

“We need to pounce on any opportunity to protect our native species,” Brewer says. “Nine lives no more for feral cats.”