Meeting Abstract
9.7 Saturday, Jan. 4 09:30 Lizard thermoregulation indices applied to the koala provide evidence for behavioural thermoregulation BRISCOE, N.J.*; HANDASYDE, K.A.; KROCKENBERGER, A.; PORTER, W.P.; KEARNEY, M.R.; Univ. of Melbourne; Univ. of Melbourne; James Cook Univ., Cairns; Univ. of Wisconsin, Madison; Univ. of Melbourne nbriscoe@unimelb.edu.au
Both ectotherms and endotherms can select microclimates or adopt postures or orientations that aid with the regulation of body temperature. The thermoregulatory behavior of ectotherms is often quantified using indices that compare body temperatures experienced by animals in the field to that of a non-regulating control moving randomly through the environment. These indices provide information about the thermal quality of the habitat and allow comparisons to be made between sites, seasons or different species. We adapt this approach for endotherms so that thermal quality of habitat (de) and effectiveness of thermoregulatory behaviour (E) are evaluated with respect to an animal’s thermal-neutral zone, rather than preferred body temperatures. We then use these indices to evaluate patterns of thermoregulatory behaviour in an arboreal marsupial, the koala Phascolarctos cinereus. We collected behavioural, microclimate, and habitat data from a southern (temperate) and northern (tropical) site, and used a biophysical model to predict energy and water costs of koalas as well as to model energy and water costs of a randomly behaving control. There was no evidence that koalas used behaviour to reduce energetic costs of thermoregulation. However they used both postural adjustment and microclimate selection to reduce heat loss requirements, remaining closer to their thermal-neutral zone than expected from the null model. Koala investment in thermoregulatory behaviour increased as the thermal quality of the habitat decreased in summer, but not in winter.
