Regulate its temperature
Like all reptiles, tortoise is ectothermic (organism with body temperature is the same as that of the external environment and is not produced by the body itself).
The tortoise depends on the outside temperature unlike endotherms (mammals and birds) who maintain constant internal temperature. She warms with the heat of the sun, it is said thermoregulation.
When it reaches a temperature between 25 and 30°C, it can fully assume its activities like eating and find partners.
Beyond these temperatures, it seeks to protect from intense sun, under bushes for example. Thermoregulation is an important activity that depends on the quality of the habitat.