Look for elusive Marbled Whiptail amid rocky soil, low vegetation on Trans-Pecos

The Marbled Whiptail (Aspidoscelis marmorata) is one of 10 species of “racerunners” that live in Texas, and like most of the species in this genus, it is quite common throughout the Trans-Pecos region of the state. It can also be observed in a diagonal swath that extends through the central portions of the Panhandle.

This intricately patterned lizard typically prefers habitats with rocky soil and low vegetation, particularly in and around rocky arroyos and rocky hillsides. It can also be seen, although substantially less frequently than other whiptail species, near residences and in parks where there is ample moisture from irrigation.

The Marbled Whiptail is an elongated reptile covered with small, granular scales of equal size along its back and sides. It is one of the larger whiptail species that occurs in Texas, rivaled in size only by the slightly larger Checkered Whiptail. Very mature adults attain a total length slightly over 12 inches; the average adult is 9-10 inches.

The background coloration is normally dark tan to brown, and the back is adorned with slightly darker vertical blotches arranged in a reticulated manner — thus the common name. The comparatively long tail, which can be up to twice the length of the animal’s body length, is a plain brown while the limbs are heavily mottled. Adult males have a dark black blotch underneath the forebody. The belly scales are much larger and plate-like in appearance.

Marbled Whiptails, like other lizard species, are “cold-blooded,” or ectothermic, meaning they do not generate heat from the inside of their body, as mammals and birds do, but are dependent on outside sources for heating and cooling. They are active throughout the day from March to November, and unlike many other reptile species, the high metabolism of this lizard enables it to be observed during the hottest part of the summer afternoons.

This species of lizard is a dietary carnivore generalist, feeding on just about any small invertebrate animal it can fit into its mouth. It feeds principally on small beetles, ants, grasshoppers and other arthropods.

The Marbled Whiptail is oviparous, which is a fancy way of saying it lays eggs. After emerging from the winter-long brumation period (reptiles do not hibernate in the true sense of the word), males search out females to mate. After mating, the female lays a small clutch of eggs (between 2 and 4) in moisture-retaining soil. Older, large females can lay two to three clutches of eggs per summer. After about two months of incubation, the delicate young, which are replicas of the adults, emerge prepared to fend for and care for themselves. 

These lizards are incredibly nervous, quite wary and exceptionally difficult to approach closely in the field. They are constantly on the move, foraging for food in the ground cover and loose soil. Occasionally they will stop to bask in between meal items, but their metabolism is such that they will begin to forage within minutes of stopping.

Their movement is based on short bursts of speed, rarely more than a few feet at a time unless they feel threatened. To observe this elusive creature, watch for it as it darts between portions of ground vegetation.

Michael Price is owner of Wild About Texas, an educational company that specializes in venomous animal safety training, environmental consultations and ecotourism. Contact him at wildabouttexas@gmail.com.