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Marsupial mouse survives fire by switching itself off

Fire-smart marsupial A little Australian marsupial survives the aftermath of bushfires by spending its days in torpor and only going out to forage during the night, say researchers.

The findings from a study of the brown antechinus (Antechinus stuartii), are published today in the Royal Society journal Biology Letters.

"There's been an increase in bushfires in Australia and we were interested in how animals survive this," says co-author zoologist Dr Clare Stawski, a post-doc researcher at the University of New England.

"Ours is the first study to find that torpor can help an animal survive the aftermath of a fire."

The brown antechinus -- also known as Stuart's antechinus and Macleay's marsupial mouse -- is preyed upon by foxes, feral cats and dogs.

Its best defence under normal circumstances is hiding in the undergrowth, which is where they catch their insect prey. But bushfires burn all the groundcover, removing any protection while foraging.

Stawski and colleagues tested the hypothesis that torpor may help the little marsupials survive predation in a burnt out landscape.

During torpor "everything switches off," says Stawski -- an animal's body temperature falls and its metabolism, breathing and heart rate slows, enabling it to save energy.

If an antechinus could save energy after a fire, it wouldn't need to go out looking for food as much so it wouldn't need to expose itself to predators.

Prescribed burn

To test this hypothesis, Stawski and colleagues compared two groups of brown antechinus in the Guy Fawkes National Park of New South Wales.

One group was in an area where the National Parks and Wildlife Service carried out a prescribed burn, while the other was in an unburnt (control) area.

The researchers used radio tracking devices to measure the animals' body temperature and movements before and after the fire.

They found that antechinus in the unburned areas foraged both during the day and night and didn't use as much torpor.

Those in the burned area remained in their home range, despite access to unburned area nearby.

"In the burned areas, animals used a lot or torpor and forage close to their nesting areas, only during the night," says Stawski.

"They have absolutely no cover so by using torpor they reduce the amount of time they have to be active because they're saving energy, which means they reduce the amount of exposure to predators."

Preliminary findings from other studies suggest that, after fires, antechinus populations are able to bounce back to the same levels as those in unburned areas.

However, says Stawski, it's important that fires are not so intense they destroy trees, which are an important safe nesting area for the antechinus during torpor.

The prescribed burn was low-intensity and wiped out ground cover but not trees, she says.

Related: Antechinus go out with a bang