The short-beaked echidna (Tachyglossus aculeatus) has the widest geographic distribution of any Australian native mammal and has not suffered the same decline post-European settlement as many mammals. Here I evaluate its field physiology in terms of the physiological characteristics that contribute to its success. Its low body temperature (Tb) and basal metabolic rate are not associated with a low field metabolic rate (FMR). Echidnas move over large distances daily, contributing to this typical mammalian FMR and despite limitations imposed by their limb structure. They spend up to 12% of their active time digging, excavating considerable quantities of soil and so are important ecosystem engineers. Echidnas moderate their activity seasonally; they are exclusively nocturnal during hot weather, moving more quickly to and from foraging sites in summer. However, despite earlier hypotheses, echidnas do have physiological heat dissipation in the form of enhanced evaporative water loss at high temperatures. South-west Australian echidnas are heterothermic, using daily torpor regularly and sometimes hibernation, but this heterothermy does not have the strong seasonal pattern observed in colder climates. Heterothermy allows echidnas to avoid unfavourable conditions; for example echidnas impacted by fire reduced their Tb and activity compared with those not affected. The echidna’s physiological flexibility is a factor contributing to their current success and presumably will aid their continued survival in the face of human-induced habitat modification and climate change.