Ecological physiology of a small arid zone marsupial in relation to its thermal environment

Abstract

The vast arid interior of Australia is home to a surprising diversity of insectivorous marsupials (Dasyuridae). The ability to enter daily torpor in a resource-poor environment possibly contributed to the success of this group. However, most of our knowledge about the energetics of dasyurids is based on laboratory work with field data being extremely scarce. Here we present a summary of one of the first field studies using radio-telemetry on the winter thermobiology of a dasyurid living in the sandy deserts of Australia. The study organism, the nocturnal Brush-tailed Mulgara ('Dasycercus blythi'), evaded daylight temperature peaks by burrowing. However, during night-time activity mulgaras were exposed to temperatures as low as -2.9°C. The activity phase was therefore centered around dusk and was usually shorter than the scotophase. Furthermore, mulgaras entered torpor frequently and, because they often used shallow burrows, they were able to reduce body temperatures (Tb) below the average soil temperatures of 16°C. Maximal torpor bout length was 12.8±6.4 hr and minimum 18.5±6.1°C (n=8). Females employed torpor throughout most of pregnancy but torpor was apparently incompatible with early lactation. Torpor in males was shorter and less frequent during the early winter mating season than during late winter.