Only the tough survive in the Sonoran Desert, and the millennia-old reptile family has adapted to the harsh landscape like no other animal. The rattlesnake may be the area’s most famous resident, with some 20 species slithering around Arizona’s rocky canyons and dusty desert floors, including the western diamondback, tiger, and sidewinder. They’re best known for their ominous rattles, a series of hollow segments made of keratin—like fingernails—that rub against one another at the end of their tails.

When threatened, the snakes strike a defensive posture and shake their tails to warn predators of their potent venom, which has an enzyme that paralyzes nerves and destroys tissue and blood cells. What is rarely appreciated about the rattlesnake, though, is its heat-sensing pits. These sensory organs near the eyes and nostrils produce a “heat image” that allows the rattlesnakes to spot prey in the pitch black of a desert night. You may also come across other desert snakes, like the banded sand snake, king snake, or gopher snake.

Lizards scurry around the desert as well, consuming insects, leaves, and springtime blossoms. Visitors are likely to see some of these harmless creatures sunning themselves on mountainsides and rocks, or even searching for shade on patios. The dozens of varieties include the Sonoran collared lizard and desert iguana, as well as whiptails, geckos, chuckwallas, and spiny lizards. North America’s only venomous lizard, the gila monster, also makes its home in Arizona.

This large reptile, which can grow up to two feet long, spends most of its life underground. The black lizards are covered in spots or bands, in shades of pink, orange, yellow, or red. A host of toads, frogs, and desert tortoises also inhabit Arizona.