Overview
Clark’s Spiny Lizard (Sceloporus clarkii) is a large, rugged, heavily armored arboreal lizard native to the oak-dotted canyons, riparian gallery forests, and desert ranges of the American Southwest and Mexico. Named in honor of American naturalist John H. Clark, it is easily recognized by its bold black wrist and ankle bands and its habit of spiraling smoothly around tree trunks to evade observers.
Biology and Physical Characteristics
Clark’s Spiny Lizard has a robust, stocky build with large, sharply keeled, mucronate (spine-tipped) scales that give it a fiercely prickly texture. Its body color is grey, olive, or greyish-brown with dark crossbars and a distinctive black collar that is interrupted on the nape. Its forelimbs bear bold, diagnostic black crossbands just above the wrists. Adult males exhibit brilliant turquoise, greenish-blue, or metallic cyan patches on their bellies and chin.
Behavior and Ecology
Unlike many terrestrial desert spiny lizards that cling strictly to boulders, Clark’s Spiny Lizard is an accomplished tree climber, spending most of its time high on the trunks and major limbs of canyon oaks, cottonwoods, mesquites, and large saguaros. When approached by a human or predator, it calmly sidesteps around the opposite side of the trunk, matching its rough spiny scales to the fissured tree bark.
Conservation and Human Impact
Classified as Least Concern by the IUCN, Clark’s Spiny Lizard has a stable, wide geographic distribution with secure populations in protected mountain canyons and riparian corridors across the Coronado National Forest in Arizona and Sierra Madre Occidental in Mexico.
Interesting Factoid
Clark’s Spiny Lizard is a master of the tree-trunk peekaboo: instead of fleeing when you walk toward it, it glides silently around to the far side of the tree trunk, keeping the tree between you and itself while peeking out with one sharp eye.