EXTREME heat is forcing Western Australia’s critically endangered western ringtail possum (Ngwayir) to cut back on vital activity and feeding, new research shows.

During the summer of 2024–25, which included several heatwaves, the research team monitored ten western ringtail possums living in woodlands near Perth.

Each animal wore a lightweight collar fitted with motion sensors to record activity levels.

The study found that on very hot days (above 40°C), nocturnal activity declined by up to 43 per cent in males and 31 per cent in females, compared with cooler days (around 27°C).

“What really stood out was that the biggest drop in activity happened early in the evening, when western ringtail possums usually do most of their feeding,” said Murdoch University PhD candidate and zoologist Roy Teale.

“That’s concerning, because it suggests they’re missing critical foraging opportunities on the hottest days, which can lead to weight loss and lower energy levels.”

Mr Teale said those changes could potentially translate to lower rates of reproduction and survivability.

“During one of the heatwaves, we lost a collared possum that likely died from heat stress, and another was found showing clear signs of overheating such as panting, shaking and licking its paws,” he said.

“It highlights just how vulnerable this species is when temperatures climb.”

The western ringtail possum is listed as critically endangered by the Environment Protection and Biodiversity Conservation Act, and it was recently believed that the species had declined by more than 80 per cent in ten years to an estimated population size of around 3400 mature individuals.

However, last year, Mr Teale led one of the largest and most rigorous wildlife surveys ever done for the species, surveying 41 sites over 1200km of transects across the Southern Swan Coastal Plain, Southern Forests and South Coast.

Researchers estimate they counted about 21,800 possums in total, nearly seven times higher than previous estimates.

“One encouraging finding from my earlier research was that western ringtail possum numbers are far higher than we previously believed,” Mr Teale said.

“But higher numbers don’t mean the species is safe. With climate change driving more frequent and intense heatwaves, our latest findings show new risks emerging that could still threaten the species’ long term survival.”

Lead author on the study and DBCA research scientist Harry Moore, recommended that future climate vulnerability assessments needed to move beyond counting deaths.

“Our results show that it’s not enough to look at whether animals survive heatwaves — we also need to understand what heat is costing them,” he said.

“Protecting cooling habitat like large trees, canopy cover and natural hollows, and factoring behavioural stress into climate risk planning, will be critical as extreme heat becomes more frequent.”

The study, a collaboration between the Western Australia Department of Biodiversity, Conservation and Attractions (DBCA), Murdoch University, the University of Western Australia and Biota Environmental Sciences, examined how extreme but non-lethal heat affects ringtail possum behaviour — an area poorly understood by scientists.

The paper, Sublethal effects of extreme heat on a critically endangered marsupial, is available in the journal Pacific Conservation Biology at www.connectsci.au