Numbats are built to handle the heat.

The stripy marsupial, Myrmecobius fasciatus, regulates body temperature through raising or flattening its fur, to save energy managing thermoregulation, since its diet of thousands of termites a day provides very little energy.

Key points:

  • A new study found numbats could only spend 10 minutes in the sun on a hot day before overheating
  • Scientists are concerned hotter days from global warming could reduce foraging time for the numbat
  • Conservation estate managers are taking greater steps to address climate change at wildlife sanctuaries

It has evolved to only operate during daylight hours, the same time its insect prey is active.

But this could soon bring challenges in a warming climate.

New research from Curtin University, published in the Journal of Experimental Biology, suggests as little as 10 minutes in the sun on hot days can result in the small mammal overheating and retreating to a burrow or hollow.

And that has scientists concerned about how well the already endangered mammal (the non-sanctuary numbat population is estimated to be about 2,700) could adapt to increases in global average temperatures.

A numbat’s body is like a thermal window allowing heat exchange by flattening or puffing up its fur.(Supplied: Christine Cooper)

Ecological physiologist Christine Cooper, lead author of the new research, said the numbats were overheating when their body reached about 40 degrees Celsius.

And this was occurring when the wet bulb globe temperature — a measurement of heat stress factoring in temperature, humidity, wind speed and several other elements — hit about 23C.

Most of the heat being absorbed was from the ground and environment around the numbats rather than just the solar heat.

This means that even after retreating to shade in hot conditions, the marsupial can continue to warm up.

Numbats retreat to the cool comfort of a hollow log or underground in hot temperatures.(Supplied: Tim Henderson/Australian Wildlife Conservancy)

Dr Cooper said it appeared that numbats already foraged in the early morning and later in the day during summer but warned global warming could change the animal’s behaviour.

“If it gets hotter and hotter the windows for foraging will get narrower and narrower,” she said.

“The rest period will need to get longer and they will be pushed to early morning and evening.

“That would expose them to predators.”

University of Melbourne ecologist Natalie Briscoe, who was not involved in the research, said it was often thought hotter weather would primarily impact animals through heatwaves, but more subtle effects were also likely to be important.

“To be able to survive in a particular place, animals like numbats need to be able to be active for enough time to get the energy, water, and nutrients they need,” Dr Briscoe said.

“While some animals like feral cats can adjust their activity timing seasonally to avoid stressful conditions during the daytime over summer, this may not be an option for more specialised species like the numbat.”

The new research was based on drive-by surveys — numbats are notoriously hard to trap as you can’t leave termites as bait and the critter has shown no taste for peanut butter or other typical lures — over 12 months.

Dr Cooper and her colleague Phil Withers drove around the Dryandra Woodlands and Boyagin Nature Reserve, about 170 kilometres south-east of Perth. They pointed a thermal imaging camera at a numbat when they spotted one.

A total of around 50 numbat videos were captured, spanning the whole year.

The numbat’s stripes were not found to have any significant thermal impacts, despite being patterned like a barbecue grill.

Dr Cooper said the next stage of the research would be climate and habitat modelling to better understand which numbat populations could be at greater risk than others from hotter weather.

Further research is also needed into how climate change might impact the behaviours of the termites the numbats eat.

An 1845 lithograph of numbats, which were once found across several states of Australia.(Supplied: Henry Constantine Richter)

Lessons for translocation

Numbats were once found across much of southern Australia including desert, woodland and more forested landscapes.

Following widespread habitat clearing, and the introduction of predators like foxes and cats, their numbers skydived.

Numbats were reduced to just two wild populations in the Dryandra Woodlands and another region of Western Australia, the Upper Warren.

Numbats need to eat 20,000 termites every day and get a lot of their water intake from consuming the insects.(Supplied: Christine Cooper)

But in the past few decades, the wild population has been bolstered with translocations to sanctuaries in different parts of the numbat’s historical range across WA, South Australia and New South Wales.

Land managers of these habitats are increasingly having to consider the impacts of climate on where they send animals and for established communities.

The WA Department of Biodiversity, Conservation and Attractions said it was taking into account longer-term factors such as climate change, habitat suitability and security of land tenure when translocating numbats.

The Mt Gibson Wildlife Sanctuary is one of several places around Australia where numbats have been translocated to create new subpopulations.(Supplied: Wayne Lawler/Australian Wildlife Conservancy)

UNSW’s Katherine Moseby is part of a project studying the effects of extreme heat at past numbat translocation sites: Secret Rocks in South Australia and the Australian Wildlife Conservancy’s Mt Gibson Wildlife Sanctuary in WA.

About 15 numbats were fitted with GPS collars and accelerometers, after being spotted and netted, which will provide more data on the kinds of shelters they use during heat waves.

“These studies provide really important field data to test biophysical models as extreme heat is likely to become a major factor structuring mammal communities in the arid and semi-arid zones,” Dr Moseby said.

“We don’t know if they can use torpor [go into a lethargic state] to save energy during hot weather down their burrows and this is something we hope to study.”

Numbats at the Mt Gibson sanctuary have been fitted with collars to monitor their conditions over summer.(Supplied: Tim Henderson/Australian Wildlife Conservancy)

Australian Wildlife Conservancy senior ecologist Jennifer Pierson said the WA project site had recorded days of 40C already this summer.

She said understanding what shelters the numbats used, and when they used them, would help with not only managing current populations but other translocations.

Numbats are just one of the five mammals the Australian Wildlife Conservancy has been subjecting to climate vulnerability risk assessments in its sanctuaries.

“We’re hoping to move from being reactionary to proactive,” Dr Pierson said.

But Dr Pierson said managers had to be careful not to make things too easy for animals, and promoting animals with the genes to adapt to the conditions was important.

A numbat taps into a tree stump seeking termites.(Supplied: Christine Cooper)

For other mammals like the golden bandicoot, this has meant breeding specimens from the Kimberley (which has the greatest genetic diversity compared to other locations) with populations elsewhere in Australia. 

“It’s about coming up with actions that hedge our bets a little bit,” Dr Pierson said.

“So having that balance of making sure we allow animals to experience the natural environment but also acknowledge as things get tougher we’re providing the support.”

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