Figure 4.

Relationship between internal, external, and soil temperatures for a male echidna during two periodic arousals and final emergence from hibernation. Internal temperature (T_b) was measured by an implanted datalogger (Onset Computer Corporation, Stowaway Tidbit) in the peritoneal cavity, external temperature from a logger (Thermochron iButtons, DS1922L; Maxim/Dallas Semiconductor, TX, USA) attached to a tracking transmitter, which was glued to the spines. Soil temperature was measured at 20 cm depth at a Bureau of Meteorology station 2 km from the field site. Redrawn from Nicol et al. (2008).