Torpor by the Honey Possum, Tarsipes rostratus (Marsupialia: Tarsipedidae), in response to food shortage and low environmental temperature.

Abstract

Tarsipes rostratus is a 5-15 g marsupial with a natural distribution restricted to shrublands and heathlands of southwestern Australia. In the laboratory, it has metabolic rates that vary from 150-350 J (g.h)-1, and does not become torpid if artificial nectar is available. When nectar is removed, animals ultimately become torpid for intervals of several hours, during which metabolic rates are often reduced by more than 90%. The time taken by animals to become torpid is reduced, and the duration of torpor bouts increased, if body size and ambient temperature are decreased. By becoming torpid under the experimental conditions imposed, animals reduce their total daily energy expenditures by approximately 70%. It is suggested that torpor occurs when the energy reserves of animals fall below a critical level. In the field, torpor is most prevalent in animals the weight less than 7 g, and occurs predominantly during the period from March to September. Evidence relating to possible causes of torpor in the field is equivocal.