Australian mammals give lesson in winter survival

Published 03 February 2009

stripe-faceddunnart

Research by UNE scientists into mechanisms used by small mammals to help them survive cold winters is making the news in a snow-bound Northern Hemisphere.

A report on research by UNE’s Gerhard Körtner and Fritz Geiser appeared last month in naturenews, an online publication of the leading scientific journal Nature.

The report refers to a forthcoming article (Körtner G., Geiser F., 2009: “The key to winter survival: daily torpor in a small arid zone marsupial”, Naturwissenschaften, in press) on the winter behaviour of desert-dwelling stripe-faced dunnarts (pictured here).

Professor Geiser and his team, working in UNE’s Centre for Behavioural and Physiological Ecology, have developed an international reputation for their studies of hibernation and torpor (a state between sleep and hibernation) in Australian mammals and birds. They have found that some Australian mammals can lower their body temperature to near 0 degrees Centigrade and reduce their metabolic rate to 1 per cent of that in active individuals.

By entering a state of torpor, animals and birds are able to conserve energy and water, significantly improving their chances of survival. About half of all terrestrial Australian mammals and an unknown number of birds use hibernation (multi-day torpor) and daily torpor in this way, Professor Geiser says.

In this latest study Dr Körtner, a Postdoctoral Fellow at UNE, observed the winter behaviour of stripe-faced dunnarts in Astrebla Downs National Park in Queensland using lightweight body-temperature monitors. The researchers found that the dunnarts entered torpor almost every night, and that the length and depth of the torpor period was dependent on air temperature.

Having studied torpor use in Australian animals for many years, Professor Geiser says it is used in a diverse range of environments. “It appears, for example, that the success of the many small carnivorous marsupials in the Australian arid zone, which even employ torpor during reproduction and development, is at least to some extent due to their extensive use of this physiological strategy,” he said.

“The rare mountain pygmy possum persists in the Australian Alps largely because of its ability to hibernate. And employment of torpor in winter allows birds to remain resident for the entire year without the need for risky migration and re-establishment of home ranges.

“Moreover, recent evidence suggests that the use of torpor, and the resulting reduction in energy requirements, can contribute to predator avoidance because less time is required for foraging. Avoidance of predators in turn increases lifespan, and results in selection of long-lived individuals and species.”

To enhance knowledge about torpor use in Australian mammals and birds, Professor Geiser and his colleagues have been awarded an Australian Research Council Discovery Grant of $250,000 for a project titled “Cool mammals: responding to thermal and energetic challenges in the Australian tropics”.