Temperature variation in nest boxes occupied by arboreal mammals during winter in southern Australia

We investigated nest temperatures in nest boxes occupied by single lactating brush-tailed phascogales (n = 8 boxes) and 1–3 adult sugar gliders (n = 7 boxes) when overnight ambient temperature dropped to <5°C. Temperature in the nest decreased or increased rapidly as animals vacated or re-occupied their nests. In the hour following first night-time departure, temperatures in sugar glider nests dropped by 9°C but only by 4°C in phascogale nests. The slower rate in phascogale nests was due to the presence of nestlings. Phascogales returned repeatedly to the nest during the night, resulting in an average 15°C differential above ambient over the night (2200–0500 h). Gliders returned infrequently during the night, resulting in an average nest-ambient differential of 3–5°C. After departure some glider nests tracked ambient to <0°C. The ability of nests to insulate and moderate temperature fluctuations requires further study. Our study highlights that we have incomplete knowledge of many aspects of the nesting ecology of cavity-using Australian mammals.