Seasonal Thermoregulation of Brush-Tailed Mulgaras (Dasycercus blythi)

Abstract

In Australia's arid zone, brush-tailed mulgaras (Dasycercus blythi) occupy burrows throughout the year, use bouts of energy/water saving torpor during the winter reproductive season, but little is known about their thermoregulation outside of winter. We used temperature-telemetry to investigate the daily body temperature (T_b) fluctuations during both winter and summer. In winter, males and females readily used torpor (males = 88.0% ± 10.6% from 150 days tracked, n = 3; females = 85.4% ± 5.8% from 151 days tracked, n = 2) and in summer torpor was rare in both sexes (males = 1.6% ± 1.9%, 163 days tracked, n = 4; females = 3.0% ± 2.8%, 157 days tracked, n = 4). The minimum winter T_b was 11.7°C (mean T_b = 23.3°C ± 4.2°C males; 19.6°C ± 5.1°C females); in summer T_b did not fall below 30°C. Torpor bouts in winter lasted for 7.1 ± 6.1 h in males and 11.8 ± 7.8 h in females; in summer torpor bouts were < 120 min in both sexes. Torpor expression differed between sexes during winter, likely due to different selective pressures, with females using deeper and longer torpor bouts than males. In summer, no sexual differences in torpor patterns were observed. Summer torpor use by mulgaras is likely crucial for energy and water conservation in the arid zone, and future conservation work should focus on summer adaptations.