In October of 2004, I spotted this Desert Tortoise (Gopherus agassizii) with a red-stained mouth from eating Engelmann's Prickly Pear fruits. Desert Tortoises get almost all of their water from the plants they eat, and juicy and tasty Engelmann's Prickly Pear fruits are a good source of moisture for them.
They are slow-moving, but wild Desert Tortoises shouldn't be handled or picked up unless it's to rescue them from imminent danger because it can severely stress them. As a defensive tactic, a Desert Tortoise will empty its bladder if picked up or stressed. These desert animals can precipitate solid urates in their bladders and then reabsorb the water in their urine, so handling them can exhaust their reserve water supply.