Fig. 3. Hibernating T_b for a male echidna (echidna 1E7C, mass range 3.2–5.2 kg; A) plotted against reference soil temperature at a depth of 20 cm (T_ref) for five hibernating seasons, and for a female echidna (echidna 006F, mass range 2.3–3.0 kg; B) for six hibernating seasons. Solid lines are regressions fitted to all data. For echidna 1E7C (A) T_b=0.65T_ref+4.3, r²=0.84; for echidna 006F (B) T_b=0.62T_ref+4.3, r²=0.82. The fact that the slopes are significantly less than 1 shows that at high T_a echidnas seek out cooler areas to hibernate, while at low T_a they move to relatively warmer areas.