Yarrow’s Spiny Lizard is a medium-sized member of the Phrynosomatidae (spiny lizard family), native to the southwestern U.S. and northern Mexico. With a maximum snout-to-vent length of around 10.5 cm (4.1 in), this lizard is easily recognizable by its keeled, overlapping scales that create a net-like torso pattern. Its base coloration ranges from gray or olive-gray with iridescent tints of pink, green, copper, and blue. A full black collar edged with a thin white line sets it apart from other species. In males, vibrant blue patches appear on the throat and belly, while females generally display muted or absent belly markings.
This species thrives in montane regions—particularly the "Sky Island" mountain ranges of southeastern Arizona, southwestern New Mexico, and beyond into northern Mexico. It inhabits elevations from roughly 4,300 ft to over 11,600 ft, living in rocky canyon bottoms, talus slopes, cliffs, boulder fields, and wooded areas like Madrean Evergreen and Montane Conifer forests.
Yarrow’s Spiny Lizard is a diurnal, rock-dwelling species that basks on sun-warmed surfaces and is typically easy to approach—though it’ll retreat into rock crevices if threatened. In cooler months, they share communal shelters in south-facing cracks and outcrops; during warmer periods, both sexes display territorial behaviors. They feed opportunistically on a wide range of insects and spiders, including grasshoppers, ants, beetles, caterpillars, and wasps.
Uniquely, the Yarrow's Spiny Lizard is viviparous—it gives birth to live young. Mating occurs in fall, and females can store sperm through winter, with births ranging from late spring to early summer depending on elevation. Litter sizes usually span 7–14 offspring, and developmental rates vary—juveniles may mature in 5 months at lower elevations, but up to 15 months at higher elevations.
With over 70% of its global range in Arizona, this species serves as an important indicator of montane ecosystem health. Its presence reflects robust riparian and rocky woodland environments. Given its limited dispersal and isolation across fragmented mountain landscapes, monitoring its populations can provide valuable insights into climate impacts and biodiversity trends in high-elevation biomes.