The energetics of basking behaviour and torpor in a small marsupial exposed to simulated natural conditions |
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Authors: | Lisa Warnecke Fritz Geiser |
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Institution: | (1) Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia |
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Abstract: | Limited information is available on basking behaviour in torpid mammals and its energetic consequences. We investigated the
effects of physiological and behavioural strategies on the energetics of the fat-tailed dunnart (Sminthopsis crassicaudata). Metabolic rate and body temperature during torpor, basking and rest were measured over 24 h in response to simulated environmental
conditions: (a) constant ambient temperature (T
a) of 15°C, (b) constant T
a of 15°C with access to a radiant heat lamp, (c) a T
a cycle (range 15–31°C), and (d) a T
a cycle with access to a radiant heat lamp. When a radiant heat source was provided, all dunnarts (n = 16) basked during all measurements, which resulted in energy savings of up to 74% during rest. Overall, torpor was used
on 59% of measurements with a maximum duration of 16.2 h and reductions in metabolic rate of 90% compared to normothermic
values. Torpid dunnarts actively moved from a shaded area to position themselves under the heat lamp with body temperatures
as low as 17.5°C and thereby reduced rewarming costs by 66%. We demonstrated, for the first time in the laboratory, that torpid
animals actively move to a heat source to bask, and that this behaviour results in considerable energy savings. Our finding
supports the view that basking during normothermia and rewarming from torpor substantially reduces energetic requirements,
which may be important for the survival of small dasyurids living on limited resources in the Australian arid zone. |
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