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Species Spotlight

Whiptail Lizards

By Doug Moore

Yaahooo! The “monsoon” is here and good soaking rains have fallen in Madera Canyon!  Our summer rains bring forth such a wonderful profusion of life! Precipitation stimulates a riot of plant growth, fodder for a legion of emerging insects. The insects in turn are grist for an array of invertebrate and vertebrate predators enticed into activity by the abundance of “tasty morsels” and the “somewhat milder, humid conditions.” Absolutely my favorite time of year in Southeastern Arizona (I’m sure the bone-dry, heat-blasting desolation of June has something to do with this…), the summer rainy season is a very productive time to wander around Madera Canyon.

Up around Proctor several times recently in late morning, I was surprised to see how many whiptail lizards were out! It seemed as if I could not walk more than 10 feet without one of these slim, agile pin-striped lizards skittering on ahead up the path or dashing headlong into trailside vegetation. Foraging naturally, Whiptails move with a hesitant, jerky “mechanical-ness” that somewhat reminds me of the robotic break-dancers on TV. But when disturbed, they can generate surprising speed from their tiny limbs, sometimes even tucking their front feet up off the ground and propelling themselves solely by the furious churning of hind legs and feet.

Two species of Whiptail lizards are commonly seen in Madera Canyon, the Sonoran Spotted Whiptail and the Desert Grassland Whiptail. The species are remarkably similar in size, description, and living habits; also, their preferred habitats overlap. It is often necessary to sneak up and take a close look to tell the two lizards apart.

Sonoran Spotted Whiptails, Aspidoscelis sonorae, are thin lizards to about 6 ½ in length, including tail. They are brown to black in color with a long brown to olive-brown tail and six yellow to cream stripes running along their neck and back. There are a few light spots sprinkled between the stripes, although the spots can fade in older individuals and may be hard to see from a distance. Found from Semi-desert Grassland up through Madrean Evergreen Woodland into Montane Conifer Forest, Sonoran Spotted Whiptails prefer hillsides, canyons, riparian corridors, and low valleys. Diurnal lizards, they are most active in the morning and late afternoon foraging on the ground for ants, termites, and other small invertebrates.

Desert Grassland Whiptails, Aspidoscelis uniparens, are also thin lizards to about 6 ½ inches in length. They are dark brown in color with a long, thin, muted blue to olive tail and six light cream stripes running down neck and back. There are no light spots between the stripes! Diurnal lizards, Desert Grassland Whiptails are most active in the late afternoons in valleys and on slopes within Semi-desert Grassland and Interior Chaparral. They eat ants, termites, and other small invertebrates.

Perhaps the most interesting fact about these two whiptail species is that they are all females! There are no males! Both species are all-female lineages that produce fertile eggs asexually; all the hatchlings are clones of the mother!

Two other whiptail species are found close to the canyon. Tiger Whiptails, Aspidoscelis tigris, with dark mottling rather than stripes, ranges from the low Santa Cruz Valley up into the bajada grasslands below Proctor and reproduce sexually. Canyon Spotted Whiptails, a lizard with a small adult striped form and a large adult spotted form, are occasionally seen along the Madera Creek corridor, primarily below Proctor; they also reproduce sexually.