The Eastern Short-horned Lizard

Text and Photo by Doug Backlund

Who can explain why one species ranges widely and is very numerous, and why another allied species has a narrow range and is rare? Charles Darwin, 1859

They go by many names: horned toads, horny toads, and horned lizards are just a few. This group of lizards, the horned lizards, is unique to western North America and Mexico. Found nowhere else in the world, thirteen species are known from western North America. Most of these species are restricted to the prairies, deserts and mountains of Mexico and the western United States. Some horned lizard species are quite rare while other are common and widespread. The short-horned lizard, Phrynosoma douglasi, is the most widespread species. Only one subspecies of short-horned lizard ranges north and east to the Northern Great Plains, the eastern short-horned lizard, Phrynosoma douglasi brevirostre. This is the only horned lizard native to South Dakota.

Horned lizards are closely related to iguanas, chameleons, and other familiar lizards, but in appearance are much different. The pancake shaped body with the hard scales and horns give horned lizards a somewhat fearsome appearance. Cryptic coloration allows horned lizards to blend in almost perfectly with the rocks and loose soils they prefer. The basic color is brown to gray, and horned lizards are able to adjust their color within this limited range to more closely match their habitat’s background color. A fringe of spines along the side of the body breaks up the outline of the animal. Almost every visible feature seems designed to camouflage these creatures from predators. In addition to cryptic coloration and habits, short-horned lizards are reported to squirt small amounts of blood from the corner of their eyes when they feel threatened. The exact function of this behavior is unknown, but some herpetologists believe it is intended to confuse predators.

Short-horned lizards usually remain motionless until almost stepped on. Then they will scurry off a few feet and freeze motionless again. When they do flee, they propel themselves in a sort of hop/run, somewhat like a toad, probably giving rise to the name "horned toad". However, short-horned lizards are not toads. Toads are amphibians and require wetlands for at least part of their existence. Short-horned lizards can thrive in habitats with no standing water. What little water they require probably comes from dew or from their food. Ants are the primary prey, but other small insects are taken also.

Although most species of horned lizards lay eggs, the eastern short-horned lizard bears live young. The young are born in thin transparent sacs that they quickly break out of. Litters of a dozen or more young are common, and up to 24 have been reported. The young resemble adults but are not armored as well. As the young grow they shed their skin repeatedly and eventually develop the horns and scales of an adult.

Short-horned lizards are found locally in western South Dakota, usually in sandy or rocky habitats. Little is known about abundance or population status. Reports indicate that short-horned lizards are present in many areas, especially in the southwest and northwest areas of the state. One of the only early reports of short-horned lizards in South Dakota came from Frank A. Patton, a state game warden in South Dakota during the 1920’s. Patton published many of his observations of wildlife. During a trip to the Slim Buttes area of Harding County on May 9, 1925, Patton observed that "sparrow-hawks were plentiful and feeding mostly on horned toads that lived among the rocks." This observation is noteworthy because it demonstrates that horned lizards, when abundant, can be an important link in the food web. More recently, eastern short-horned lizards have been reported from Fall River County, Lawrence County, Harding County, and as far east as Stanley County.

Horned lizards have fascinated many cultures over the centuries. Native American cultures symbolized horned lizards in ceremonies, stories, petroglyphs, and in other art work. Today, human fascination with horned lizards is sometimes detrimental. Wild horned lizards are often taken home in the hope of making a good pet for the kids. Unfortunately, horned lizards don’t do well in captivity. In most cases, the pet soon dies. In some of the more populated western states, collecting of horned lizards has become a major problem. Several states now limit or prohibit the collecting of horned lizards. The best practice is to enjoy these animals in their natural habitat and then leave them there.

Populations of horned lizards have been decimated in some areas because of over collecting, loss of habitat, and indiscriminate use of pesticides. Attempts to control an introduced ant, the red fire ant, may have had a major impact on horned lizards in Texas and other southern states. Red fire ants were introduced into the United States from South America between 1918 and 1930. These are highly aggressive ants that inflict numerous, painful bites on any animal, including people, that disturbs their colony. By 1958, a public outcry for eradication of the red fire ant led to the widespread use of the insecticides heptachlor and mirex. However, by the 1970’s, both chemicals were banned from use, partly because of the tremendous loss of native ants and other non-target animals but mostly because of threats to human health. Horned lizards, which prey primarily on ants, were especially affected by the efforts to control the red fire ant. Today, the Texas horned lizard (Phrynosoma cornutum) is gone from most of eastern Texas where it was formerly common, and the campaign to control red fire ants is at least partly to blame.

Anyone who is interested in horned lizards, their biology and conservation, is encouraged to contact The Horned Lizard Conservation Society, PO Box 122, Austin, Texas 78767. The Horned Lizard Conservation Society also has a page on the World Wide Web at http://www.hornedlizards.org/. The purpose of this society is "to document and publicize the values and conservation needs of horned lizards, to promote horned lizard conservation projects and to assist with horned lizard management initiatives throughout their ranges."

Meanwhile, keep a sharp eye out next time you are hiking in western South Dakota. You might spot one of the eastern short-horned lizards. If you do, try to imagine yourself in its life. How would you survive to the next day? The next year? Natural selection has answered these questions for the eastern short-horned lizard over the ages, as a species, not as individuals. Individuals live and die, but the species survives, adapting to a relentlessly changing land. The animal you see is the result. They are unique, fascinating, and deserve our respect.

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