Elation over the recent rediscovery of the threatened western quoll in the Perth Hills is fading amid revelations toxic rat poison has been found in local populations.
A new Edith Cowan University-led research paper has found first and second generation anticoagulant rodenticides in the livers of five of Australia’s largest marsupial carnivores, including WA’s western quoll (chuditch) and Pilbara northern quoll.
The Western Quoll (Dasyurus geoffroii), also known as the Chuditch is a vulnerable species, whose distribution is now confined to south-western Western Australia.Credit: Ted Mead via Getty Images
While the impact of this type of common rat poison on “non-target” wildlife species has been recorded worldwide, this is the first evidence of it in native Australian marsupial carnivores.
Of the 52 test subjects, 26 tested positive for anticoagulant rodenticides, with 11 of those having more than one compound and two – including a dead chuditch found in Gooseberry Hill – found with more than three.
The chuditch was exposed to 1.7 mg/kg of anticoagulant rodenticides including brodifacoum, difenacoum and warfarin – a dose several times higher than a lethal dose, and the highest dosing found in the study.
Another dead chuditch found in Bateman also tested positive for two of these poisons.
West Australian zoologist and Birdlife WA researcher Michael Lohr said despite the best efforts of conservation groups and the government alike to bring the species back from the brink, the study’s results foretold a grim future.
“These chemicals are quite persistent, and they can sit in biological tissues for a really long time, they’re able to bioaccumulate and biomagnify up the food chain,” he said.
“The predatory mammals that sit at the top of the food chain are at substantial risk from some of these more persistent second-generation products, and we may be really impeding their ability to come back, even when we’ve removed a lot of the traditional threats.”
First-generation anticoagulant rodenticides, known as multi-dose anticoagulants, need to be consumed in several consecutive feedings for a lethal dose and so are considered to have less chance of secondary poisoning in non-target animals.
Second-generation anticoagulant rodenticides are referred to as ‘single-dose anticoagulants’, meaning a single dose can be lethal making them substantially more potent with a higher risk to non-target animals.
Some of the anticoagulant rodenticides approved for use by Australia’s pesticide regulator, and commonly found in big-brand hardware stores, are bromadialone, brodifacoum, difenacoum, coumatetralyl, difethialone, flocoumafen, pindone and warfarin.
Australia is one of the last countries to ban or regulate the use of first and second generation anticoagulant rodenticides with the United States, Canada, the UK and most EU countries having restrictions on where they can be used and who they can be sold to.
“Right now my son, who’s 11, can go down to any hardware store or grocery store and buy as much of that stuff as you want,” Lohr said.
“So we’re really out of sync with even what the global norms are at this point in most other developed nations, and increasingly, our regulations are falling behind even developing nations that are starting to put in restrictions about sales.”
It is not the first time Lohr, whose PhD investigated the role of rodenticides in the decline of boobook owls, has lobbied the Australian Pesticides and Veterinary Medicine Authority to take restrict the widespread sale of these poisons.
In July 2024 Lohr and ECU’s Rob Davis, who was another senior author on this paper, and an entourage of zoologists, ecologists and environmental scientists from around Australia took their case to Canberra.
But despite the APVMA beginning a review of the approved status of anticoagulant rodenticides in late 2021, an expected December 2024 proposed decision was further delayed until late April. The review has still not been published.
A spokesperson told WAtoday the regulator applied robust scientific risk assessments during the reconsideration process.
“The APVMA may revise estimated timeframes for the release of regulatory decisions based on the complexity of required assessments, or the need to consider additional information,” they said.
“The predicted timeframe for the proposed regulatory decision for anticoagulant rodenticides was revised … due to the complexity of ongoing assessments.”
Chuditch are a threatened species under state and Commonwealth legislation, classified as ‘likely to become extinct’ in the wild and specially protected under the Wildlife Conservation Act 1950.
Instead of waiting for national regulation changes, local government authorities are taking matters into their own hands by no longer providing second-generation rodenticides for the community, and requiring staff and contractors to use first-generation rodenticides.
This movement, dubbed “owl friendly”, started in Margaret River, has now spread to more than nine councils including Melville, Denmark, Nannup, Mundaring, Bayswater, Cockburn, Fremantle and East Fremantle.
Birdlife Australia has started a petition calling on the APVMA to better regulate the domestic sale of second generation anticoagulant rodenticides.
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