Many small animals, such as bats and mice, eat cactus in the dessert. Insects, such as bees and butterflies, drink the nectar of the cactus flower.
Reptiles eat cacti and their flowers. The collared peccary, a type of hog, eats the prickly pear cactus. The jackrabbit normally eats grasses, but it will eat cacti during droughts. Cacti are a good source of water, as they retain fluid within their pulp. Cacti also produce fruit, which is generally safe to eat.
People may also eat cacti. The DVD series "Stay Alive" shows how to survive on cacti when stranded in the desert.