Australian marsupial predators face a threat due to rodent control measures.

Scientists worldwide have repeatedly documented the deaths of wild animals due to rodenticides—agents used for rodent extermination, commonly referred to as rat poisons. In some cases, poisoning from these substances can lead to population declines. Second-generation anticoagulant rodenticides are particularly hazardous for wildlife. Due to their long half-lives, they accumulate in the food chain and affect not only rats and mice but also some higher predators, including scavengers.

Given the limited research on the effects of rodent control substances on Australian mammals, biology and conservation specialists from several universities in the country decided to investigate the issue more thoroughly. Their article was recently published in the journal Science of the Total Environment.

The researchers analyzed the liver tissues of five of Australia's largest carnivorous marsupials for the presence of rodenticides such as bromadiolone, brodifacoum, difenacoum, kumatetril, difethialone, flocoumafen, pindone, and warfarin.

The bodies of 52 deceased animals were provided by volunteers and staff from conservation organizations. Among those studied were 20 Tasmanian devils (Sarcophilus harrisii) and representatives of four species of spotted quolls: Dasyurus hallucatus, Dasyurus geoffroii, Dasyurus viverrinus, and Dasyurus maculatus. All of these are classified as rare or close to being vulnerable.

Traces of rodenticides were found in samples from 26 animals (50%). In the tissues of 11 individuals, more than one type of rodenticide was detected, and in the bodies of two carnivorous marsupials, three types were found. Sublethal doses of poison were identified in nearly one-third of the subjects, and 17.3% of the animals likely died from rodent control substances.

The researchers suggested that due to the severity of rodenticide effects, they may threaten the populations of endangered species. Through population viability modeling, the scientists established that if juvenile mortality of Tasmanian devils increases by 15-30%, their extinction probability would rise from 29% to 100% in less than 100 years.

Since lethal levels of rodenticides were found in 5% of the studied Tasmanian devils, and potentially high toxicity in 10%, the impact of such substances could directly increase the mortality of these predators by 15%. The specialists concluded that spotted quolls are also in a vulnerable position due to the use of rat poisons by humans.

The scientists urged the country's authorities to restrict the sale of such products, following the examples set by Europe and North America, and encouraged Australian residents to use less harmful types of rodenticides for wildlife.