What physiological characteristic is suggested to help echidnas persist across temperature extremes?

Answer

Extremely low resting metabolic rates or superb control over body temperature

The ability to coexist across extremes suggests a highly efficient physiological makeup, likely involving extremely low resting metabolic rates or superb control over body temperature.

What physiological characteristic is suggested to help echidnas persist across temperature extremes?
locationhabitatmammalMonotremeechidna