One of the 30 species of garter snake native to North and Central America, the Mexican garter snake (Thamnophis eques megalops) is an aquatic snake found in Arizona, New Mexico, and Mexico. Its primary habitat is southwest riparian areas with permanent water, dense vegetative cover and an abundance of native prey, including fish and leopard frogs.

With the decline of riparian habitat in the Southwest to less than 10% of its pre-European extent, the Mexican garter snake has declined to near extinction in the U.S. This decline has been furthered by the introduction and rapid spread of the inexorable bull-frog, which has been eating its way through the aquatic fauna of the Southwest, including the Mexican garter snake itself and most of its native prey species.

photo by Philip C. Rosen

Many people fear snakes and the snake is often portrayed negatively. The most obvious example is the bible and the story of the snake that tempted Eve to bite the apple. This has not always been the case, however. In many cultures, snakes have been seen as symbols of fertility, healing and the power of gods. Our symbol of medicine, for example, is the caduceus, which is a wing-topped staff, wound with two snakes. The Greek god Hermes carried a caduceus.

A clinical fear of snakes is called ophidiophobia and for some people can be so acute that they won’t go outdoors. Studies have found that fear of snakes is in part genetic, transferred from one generation to the next. Other studies, however, have found that fear of snakes is greater in older people than children, suggesting a learned component. E.O. Wilson observed that: “the mind is primed to react emotionally to the sight of snakes, not just to fear them but to be aroused and absorbed in their details, to weave stories about them.” With proper education, people’s natural captivation for snakes can likely be turned from fear to fascination.

Despite people’s fears, most snakes are harmless and even venomous snakes rarely strike. The Mexican garter snake, like other garter snakes, is non-venomous and shy, and thus poses no risk to humans. Instead, it is a vital component of the food chain and forms an important part of what makes the Southwest unique.

Today, the Mexican garter snake is limited to an estimated 19 populations in Arizona and New Mexico, most of which consist of one to a few animals and are isolated from other populations. Threats to its habitat include livestock grazing, urban development, groundwater pumping, exotic species and illegal collection and persecution. Although the species occurs in a larger range in Mexico, many of these same threats are present and populations are poorly studied.

In response to the imperiled status of Mexican garter snake, the Center for Biological Diversity filed a petition on 12-15-2003 to list the species as threatened or endangered under the Endangered Species Act. The petition seeks protection of the snake’s habitat from livestock grazing and other threats, establishment of minimum instream flows in Southwest rivers, prohibitions on further introductions of non-native fish and amphibians, and more funding for research and removal of non-natives. These actions are likely to benefit the myriad other species that are imperiled by the loss and degradation of Southwest rivers and streams.

graphic Andrew Rodman ©2002
January 15, 2004
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