Intraspecific differences in behaviour and physiology: effects of captive breeding on patterns of torpor in feathertail gliders

Studies on the physiology of mammals and birds are often conducted using ca ptive-bred individuals and it is commonly assumed that the resulting data a re representative of individuals living in the field. To investigate whethe r these assumptions are justified, we quantified morphological, behavioural , and physiological variables of the small marsupial feathertail glider (Ac robates pygmaeus). We compared three populations: (i) individuals from a co ol-temperate, montane area, (ii) individuals form a subtropical, coastal ar ea, and (iii) captive-bred individuals. Captive-bred gliders differed from the montane field gliders in morphology (longer tails and snouts), behaviou r (longer activity periods) and physiology (less frequent torpor, shorter t orpor, shallower torpor, higher metabolic rates during rest and torpor, and slower rates of rewarming). Most of these differences were also apparent b etween the captive-bred and the coastal field gliders. Unlike both field po pulations, captive-bred gliders often became hypothermic and were unable to rewarm. In contrast to the other physiological variables, the minimum body temperatures defended during torpor and the corresponding air temperatures differed between the montane and coastal field gliders, but were similar i n coastal field and captive-bred gliders. Our study shows that morphology, behaviour and physiology can be strongly affected by breeding in or acclima tion to captivity. The poor expression of torpor and thermal performance of the captive-bred gliders raises the question of whether they possess the p hysiological capability for survival in the wild. Even though captive breed ing appears to have only minor effects on some physiological variables, dat a from captive-bred individuals should only be extrapolated to the held wit h caution.