Eastern pygmy-possums (Cercartetus nanus) are known to be conservative with energy use probably because they rely on food that varies in availability. We quantified how nest use, huddling, and torpor contribute to a reduction of energy expenditure in C. nanus during mild cold exposure. In comparison to normothermic resting C. nanus at the same ambient temperature, nest use reduced energy expenditure on average by ~17%, huddling as a pair in a nest by ~50%, whereas torpor, which was employed by all seven individuals, lowered energy expenditure by >95%. Our study shows that while all energy-conserving strategies employed by these possums can contribute significantly to reducing energy expenditure, torpor is by far the most effective because it not only reduces thermoregulatory energy costs, but also energy expenditure required for maintenance processes.
