Since reptiles have metabolic rates about one tenth that of mammals or birds, thermal support is vital for ill lizards. It is necessary to maintain critical cases at the upper end of their [[Preferred optimum temperature zone|POTZ]] with a temperature gradient. | Since reptiles have metabolic rates about one tenth that of mammals or birds, thermal support is vital for ill lizards. It is necessary to maintain critical cases at the upper end of their [[Preferred optimum temperature zone|POTZ]] with a temperature gradient. |