Reptiles
Except for small lizards, reptiles are not much in evidence in the monument. Nevertheless, they are present and are important in the various plant-and-animal communities in which they live. Almost all lizards are insectivorous, and along with birds and other insect-eaters help to keep the number of insects within bounds. A notable exception is the GILA (HEE-lah) MONSTER, (See [appendix] for scientific names of reptiles) largest of the lizards found in the United States. (It is one of the world’s two poisonous lizards, and the only one found in this country.) The gila monster is especially fond of bird eggs, and also eats nestlings and small rodents, obtaining necessary moisture from their body juices. These food habits are quite similar to those of the several species of snakes found in the monument, the majority of which are perfectly harmless to humans.
The short-horned lizard, more cold-tolerant than the desert horned lizard, ranges from the foothills into the mountain forests of Saguaro.
Just as the lizards help to control the insect population, the snakes are important in preventing the buildup of large numbers of rodents that would result in widespread damage to vegetation. Visitors to the monument rarely have the opportunity to observe snakes, since they are in hibernation during winter and remain in the shade or in underground burrows during the hot part of each summer day. Perhaps those most frequently seen are the GOPHER SNAKE and the COACHWHIP. Many desert snakes hunt only at night; others that are normally active during days of moderate temperatures become night hunters during hot weather. Although they are not abundant, there are several kinds of rattlesnakes in the monument, the commonest desert species being the WESTERN DIAMONDBACK and MOHAVE RATTLESNAKES. Except for the small, very rare, and secretive ARIZONA CORAL SNAKE, rattlesnakes are the only poisonous snakes in the monument. Snakes, like other living things in the national monument, are protected by law.
Don’t be surprised while following a desert footpath to come upon a plodding tortoise. This bona fide desert dweller, the DESERT TORTOISE, is a vegetarian, feeding on cactus, grass, and other low-growing plants.