Clark’s Spiny Lizard, Sceloporus clarkii

Clark’s Spiny Lizard, Sceloporus clarkii. Photographs taken within a residential community in the greater Alamos area, Alamos, Sonora, May 2018. Photographs and identifications courtesy of David F Smith, Alamos, Sonora.

Clark’s Spiny Lizard, Sceloporus clarkii, is a member of the Phrynosomatidae family of North American Spiny Lizards. The Phrynsomatidae family has one hundred thirty-six members placed in nine genera. There are one hundred fourteen species are in the Sceloporus genus. Clark’s Spiny Lizard consists of four subspecies: the El Fuerte Basin Spiny Lizard, Sceloporus clarkii uriquensis,; the Plateau Spiny Lizard, Sceloporus clarkii vallaris, the Sonoran Spiny Lizard, Sceloporus clarkii clarkii, the Southern Clark’s Lizard, Sceloporus clarkii boulengeri, and the Plateau Spiny Lizard, Sceloporus clarkii vallaris). Clark’s Spiny Lizard is known in Mexico as Lagartija Espinosa de Clark and Lagartija Espinosa Del Noroeste.

Clark’s Spiny Lizards are medium-sized, measuring up to 12.5 cm (5.0 inches) in snout-to-vent length and weight on average of 34.8 g (1.2 oz). They are covered in keeled, pointed scales. Their color ranges from gray to tan with scattered turquoise scales on their back and sides. Dark brown scales mark their back in a vague banded pattern. They have a dark band of scales, or collar, that lies under or around their neck. Distinct cross bands mark their forelimbs and they have a long, slender tail. Sexual dimorphism is displayed with males possessing vivid blue throats and underbellies. During the breeding season, females develop orange to red heads. 

Clark’s Spiny Lizards are arboreal and crepuscular. They are frequently observed in the cool of the morning basking on tree trunks or rocks. They often bask oriented head-downward, searching for insects at a height of 1 m (3 feet 3 inches) 2 m (6 feet 6 inches) on ash, cottonwood, oak, sycamore, walnut, and other large trees. Later in the day as temperatures rise, they often ascend into the canopy where they have been observed on branches as high as 40 m (130 feet). In some areas, they make their homes on massive boulders. Clark’s Spiny Lizards have a broad diet that includes ants, beetles, butterflys, grasshoppers, moths, spiders, and moths. Occasionally, they prey upon the Ornate Tree Lizard , Urosaurus ornatus. Their mating season lasts approximately from April to October, and females reach sexual maturity at 22 months of age or a snout-to-vent length of 9 cm (3.5 in). Only one clutch is produced each year, which is deposited in June and consists of an average of 20 eggs. Clark’s Spiny Lizard is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

Clark’s Spiny Lizard may be confused with the Desert Spiny Lizard, Sceloporus magister (larger in size, and males have a black, deep purple, or red mid dorsal longitudinal stripe that is bordered by light stripes; lack the cross bands on the forelimbs found in Clark’s Spiny Lizard. 

From a conservation perspective, Clark’s Spiny Lizard is currently considered to be of Least Concern due to their relatively large area of occupancy, number of subpopulations, and overall population size. No major threats have currently been identified for this species.