Fig. 4. Frequency distribution of T_b values from six echidnas (five female, one male, black bars) and T_ref (grey bars), in May and July. In May the majority of T_ref readings (70%) were in the range 9–12°C, as were 70% of T_b readings, but T_b values below 9°C are under-represented (4%) compared with T_ref (17%). In July the distribution of T_b values is significantly offset compared with T_ref. 58% of recorded T_ref values were between 6 and 8°C, but 62% of T_b values were between 8 and 10°C.