The effect of temperature on the pattern of torpor in a marsupial hibernator

Abstract

Physiological variables of torpor are strongly temperature dependent in placental hibernators. This study investigated how changes in air temperature affect the duration of torpor bouts, metabolic rate, body temperature and weight loss of the marsupial hibernator Burramys parvus (50 g) in comparison to a control group held at a constant air temperature of 2 degrees C. The duration of torpor bouts was longest (14.0 +/- 1.0 days) and metabolic rate was lowest (0.033 +/- 0.001 ml O2.g-1 x h-1) at 2 degrees C. At higher air temperatures torpor bouts were significantly shorter and the metabolic rate was higher. When air temperature was reduced to 0 degrees C, torpor bouts also shortened to 6.4 +/- 2.9 days, metabolic rate increased to about eight-fold the values at 2 degrees C, and body temperature was maintained at the regulated minimum of 2.1 +/- 0.2 degrees C. Because air temperature had such a strong effect on hibernation, and in particular energy expenditure, a change in climate would most likely increase winter mortality of this endangered species.

An evaluation of small-mammal use of constructed wildlife crossings in ski resorts

“…The major limiting factors for persistence and recovery of the species are the very small areas of suitable habitat and the apparent requirement of an insulating cover of snow to enable successful hibernation for up to seven months of the year (Geiser & Broome 1991, 1993Broome & Geiser 1995;Körtner & Geiser 1997;Walter & Broome 1998, Broome et al 2013). …”

“…In Charlotte Pass Village (Kosciuszko), hibernacula were often outside the normal summer habitat, indicating potential seasonal differences in habitat requirements (Körtner & Geiser 1998). Animals have very specific thermal requirements for their hibernation and have been found to frequently change their hibernacula during the hibernation period, suggesting that hibernacula differ in quality (Geiser & Broome 1993;Körtner & Geiser 1998). The best hibernacula occur in deep boulderfields with an insulating layer of snow.…”

“…The Mountain Pygmy-possum hibernates during the coldest months of the year, beginning in March/April as temperatures drop sharply and food supplies decline, and lasting until September/October, with emergence broadly coinciding with a rise in temperature and the disappearance of snow, the arrival of Bogong Moths and the spring equinox (Geiser & Broome 1993;Mansergh & Broome 1994;Körtner & Geiser 1998). Hibernation consists of periods of torpor, during which the body temperature drops to a minimum of 2 o C, and metabolic rate is substantially reduced, interspersed with periods of arousal ranging from a few hours to several days (Geiser & Broome 1991;Broome & Geiser 1995;Körtner & Geiser 1998).…”

“…Hibernation consists of periods of torpor, during which the body temperature drops to a minimum of 2 o C, and metabolic rate is substantially reduced, interspersed with periods of arousal ranging from a few hours to several days (Geiser & Broome 1991;Broome & Geiser 1995;Körtner & Geiser 1998). Optimal energy conservation occurs when the micro-climate in the hibernacula is around 2 o C, with temperatures above and below this resulting in increased energy expenditure due to increased metabolic rates and more frequent arousals from torpor (Geiser & Broome 1993). Snow melt allows the possums access to Bogong Moths that migrate to the boulderfields in September-October to aestivate.…”

Ecological consequences of temperature regulation: Why might the mountain pygmy possumBurramys parvusneed to hibernate near underground streams?

“…32 We base our calculations of overall energetic costs of replenishing evaporated water on there being 20 arousals during the hibernation period, 33 and the assumption that possums must replace the equivalent of between 1 and 10% of their body mass (5% being most likely; refs. 16 and 31) in water during each arousal.…”