The desert horned lizard (Phrynosoma platyrhinos) is a species of phrynosomatid lizard native to western North America. They are often referred to as "horny toads", although they are not toads, but lizards.

Distribution

They typically range from southern Idaho in the north to northern Mexico in the south. These lizards can generally be found in areas with desert climates throughout western North America.

Changes in the environment due to climate change can trigger shifts in the geographic ranges of animals. Phrynosoma platyrhinos has experienced some changes after the Last Glacial Maximum (LGM) which ended approximately 21,000 years ago. The end of the LGM resulted in the expansion of deserts throughout western North America, and with that expansion Phrynsoma platyrhinos had more areas suitable for them to live in. At the end of the LGM P. platyrhinos was able to expand north into the Great Basin, which is now part of their current geographical range.

Subspecies

There are two subspecies which are found in a different geographic ranges: the northern desert horned lizard (Phrynosoma platyrhinos platyrhinos) ranging in Idaho, Wyoming, Utah, Nevada, the Colorado front range, and parts of southeastern Oregon; and the southern desert horned lizard (Phrynosoma platyrhinos calidiarum) ranging in southern Utah and Nevada to southeast California, western Arizona, and northern Baja California.

Description

There are several important characteristics that can be used to identify desert horned lizards from other horned lizards. Horned lizards can be distinguished from other lizards by the large pointed scales that protrude from the back of their heads, giving them the appearance of having horns, as well as the flat and broad shape of their bodies.

This species of lizard has a distinctive flat body with one row of fringe scales down the sides. They are a medium sized lizard and can grow up to approximately 3.75 inches (95 mm) in size. When they find an area of soft sand, they usually shake themselves vigorously, throwing sand over their backs and leaving only their head exposed. This allows them to hide from predators and await their unsuspecting prey.

Habitat

Found in extremely diverse habitats. The flat-tailed horned lizard occurs in areas of fine sand, while the short-horned lizard (P. douglasii) is found in shortgrass prairie all the way up into spruce-fir forest. The most common species in the Arizona Upland subdivision is the regal horned lizard (P. solare), which frequents rocky or gravelly habitats of arid to semiarid plains, hills and lower mountain slopes. The desert horned lizard (P. platyrhinos) is found mostly in the Sonoran and Mojave deserts. It can be found in southeastern Oregon, California, western Arizona Utah, Idaho and Nevada. Outside of the United States it is found in Mexico, northwestern Sonora, and northeastern Baja California. They have a preference for places that they can find shrub covering with an understory. Phrynosoma platyrhinos will often bury themselves in sand soil, if possible, or they will live in burrows that were constructed by other animals.

The desert horned lizard has also been observed to exhibit rain-harvesting behavior in the wild, a behavior previously only attributed to a handful of other species. When rain-harvesting the lizard adopts specific posture in order to get its mouth closer to the ground.

Like other iguanids P. platyrhinos performs a number of displays. Iguanid displays are usually used to assert a social structure or for aggression and courtship, and can present in a variety of different behaviors such as: push ups, bobbing of the head, tail movements, along with changes in posture. In P. platyrhinos these displays are less aggressive and appear to be most concerned with sex and species recognition.

These behaviors include various tail positions such as curled, between the legs, or arched down with scratching behaviors, push ups, and a three-legged stance where one of the hind legs is held off the ground and the back is presented to predators.

See also

  • Texas horned lizard

References

Further reading

  • Hylton, Brodie; Ecology and Species Comparisons of the Short-Horned Lizard (Phrynosoma douglassi) and the Desert Horned Lizard (Phrynosoma platyrhinos), from the following website: [http://darkwing.uoregon.edu/~titus/herp/documents/hylton.html]
  • Arizona-Sonora Desert Museum (http://www.desertmuseum.org/books/nhsd_horned_lizard.php)