Torpor: a neat survival trick once thought rare

To enter torpor, an animal decreases its metabolism, reducing its energy requirements. A torpid animal will often be curled in a tight ball in its nest and look like it's sleeping.

Once thought to occur only in birds and mammals in the Northern Hemisphere where winters are more pronounced, we now know torpor is widespread in small Australian mammals, and has also been observed in many small Australian bird species.

Birds and mammals are endotherms and can maintain a high and constant body temperature independent of the environmental temperature, thanks to their high metabolic rate. This allows them to be active across a wide range of environments.

The downside? This high metabolic rate requires a lot of food to fuel it. By reducing the metabolism in a very controlled manner and entering torpor, an animal can live on less energy.

Torpor is an extremely effective survival strategy for small endotherms.

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Credit: Chris Wacker

A torpid eastern pygmy possum. Note the curled posture.

Animals that use daily torpor can do so for approximately 3-6 hours a day as needed.

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Sleeping Torpor Hummingbird