Whiptail lizards

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Whiptail lizard.

One spring, we raised the cement block wall that encloses our yard. Soon after the builders had finished, I saw the first lizard of the year, stretched out in the sun on the vertical face of the wall as if gravity had no hold on her slight body. I borrowed Richard’s binoculars for a closer view. Just about five inches long, the lagartija (little lizard) was faded brown all over, and marked head to tail with cream-colored stripes, each paralleled by a precise line of tiny, yellow dots. The lizard’s hind legs were huge, and her tail extravagently long.

The lizard was probably a New Mexican whiptail lizard, a species of small lizards mostly confined to the Rio Grande valley from northern New Mexico to northern Chihuahua, Mexico. Whiptail lizards, named for their long, whiplike tails, are hyperactive. Constantly in motion, whiptails dash across the ground from shrub to shrub - often running upright on their hind legs like miniature dinosaurs. They forage ceaselessly for termites and other ground-dwelling insects and spiders, swiveling their head rapidly from side to side, sniffing the air with their slender, forked tongue, and probing under surface debris with their pointed snout.

Whiptails’ hyperactivity serves as a defense also. Their alertness, speed, and agility help them outmaneuver predators like thrashers, roadrunners, Gila monsters, and snakes. These zippy lizards can sprint up to fifteen miles per hour, as fast as a roadrunner. Whiptails also escape capture by forfeiting their tails: When grasped, their tail breaks easily along a fracture plane in the vertebrae. The disembodied tail wriggles violently, startling and distracting the predator so that the lizard can dash to safety. Imagine a predator’s surprise at grabbing for a juicy lizard and instead scoring only a wriggling tail!

I called the New Mexican whiptail sunning on our new wall “she” for good reason. Along with five other whiptail species living in the Southwest, New Mexican whiptails are all-female - no males have yet been found. A product of hybridization between two other species, these unisexual whiptails reproduce by cloning themselves - producing eggs, and hence more female lizards, without mating at all.

Both dangers and advantages are inherent in this reproductive stragegy. Since the unisexual lagartijas are genetically identical, disease or inherited defects could wipe them out. However, just one lizard is required to found a dynasty, giving them an edge in colonizing newly disturbed habitats. By reproducing incredibly rapidly - they out-multiply “normal” lizards by a factor of two - the all-female species quickly outnumber competitors.

I see the New Mexican whiptail frequently. Once, when I was working near her section of wall, I turned over a rock, exposing a cockroach. She darted down, snatched it with her long tongue, and swallowed it. This largatija is a good neighbor indeed!