The numbat Myrmecobius fasciatus is a medium-sized (550·g) marsupial found only in areas of open woodland in the south-west of Western Australia, although prior to European settlement it inhabited open woodland, grassland and desert

(550·g) marsupial found only in areas of open woodland in the south-west of Western Australia, although prior to European settlement it inhabited open woodland, grassland and desert across much of southern Australia (Friend, 1993). Unlike other marsupials, numbats are exclusively diurnal and they feed only on termites collected from shallow sub-surface soil galleries. Their daily activity pattern has been related to the mainly diurnal activity of termites in these subsurface galleries (Friend, 1982). Solar heat gain (SHG) is a potentially important factor in the energy budget of a diurnal animal (Walsberg, 1988a). If numbats can exploit solar heat to aid in thermoregulation, then they can reduce their metabolism at ambient temperatures (Ta) below the thermoneutral zone. This may be particularly significant for a mammal feeding exclusively on poor quality food, such as termites, which have a low energy density and variable availability (McNab, 1984, 2000; Redford and Dorea, 1984; Anderson et al., 1997). There are anecdotal reports of numbats sun basking, especially on cold winter mornings (Calaby, 1960; Friend, 1993), suggesting that SHG may indeed have an important thermoregulatory role for the numbat. SHG by mammals is determined by a complex array of factors, including selection of microhabitat and orientation to incident radiation (Walsberg, 1988a). For mammals that have an insulating covering of fur, the pelt plays an important role in thermoregulation, influencing both passive heat loss and radiative heat gain (Walsberg, 1988b). Consequently, the biophysical characteristics of the pelt, including insulation, structure, colour, hair spectral properties and skin colour, are all important determinates of heat balance for a mammal (Walsberg, 1988b). This study investigates the biophysical properties of the numbat’s pelt in relation to insulation and SHG and assesses the thermoregulatory importance and potential for energy conservation of exploiting solar heat for this unusual, diurnal, termitivorous marsupial.