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The Return of a Rare Predator
by Jeff Servoss and Tom Buckley
Photo Credit: USFWS
The northern Mexican gartersnake (Thamnophis eques megalops) lives in dense vegetation along the banks or in the shallows of wetlands (cienegas and stock tanks) in Arizona. Historically, this non-venomous snake lived in perennial rivers, intermittent streams, and isolated wetlands throughout the southern half of the Grand Canyon State, in extreme western New Mexico, and Mexico's Sierra Madre Occidental and Mexican Plateau. In the U.S., the snake, which grows to 44 inches, is now confined to just a handful of places in Arizona—the middle/upper Verde River drainage, middle/lower Tonto Creek, the San Rafael Valley, the Bill Williams River, and a few isolated wetland habitats and stream reaches in the southeastern part of the state.
The northern Mexican gartersnake has declined primarily from interactions with non-native bullfrogs, crayfish, and non-native spiny-rayed fish. The non-native species both prey on and directly compete with the gartersnake for resources. In addition, human activities that diminish surface water or degrade riparian (streamside) vegetation are also significant threats, but especially where they occur in the presence of non-native species. The gartersnake gained Endangered Species Act protection in July 2014 as a threatened species. Efforts to control non-native predators and restore native aquatic and riparian communities could significantly benefit the gartersnake and a suite of other imperiled native fish and amphibian species throughout their range.
On May 16, 2014, as part of a multi-partner, collaborative conservation effort to benefit the species, 36 juvenile and sub-adult northern Mexican gartersnakes were released into the wild on the Bureau of Land Management's Las Cienegas National Conservation Area in southern Arizona.
The gartersnakes released at Las Cineagas were originally born, raised, and cared for at the Arizona-Sonora Desert Museum—one of the world's premier "living" museums. Captive snakes in the propagation program are fed a diet of fish and amphibians, and induce brumation (a hibernation-like state for cold-blooded animals) seasonally to promote reproductive hormones and behaviors. This program was initiated in 2006 with the inception of the Gartersnake Conservation Working Group, a coalition representing 26 different public, private, and academic institutions in Arizona and New Mexico, dedicated to collaboratively working together to identify and implement opportunities for conservation and recovery of the northern Mexican gartersnake.
On the scheduled day of the release, the snakes were measured and marked for record-keeping and identification, should one or more ever be incidentally recaptured in the wild. They were released at two wildlife ponds and a segment of the upper Cienega Creek where permanent pools support an active prey base. Because each release location has previously been the focus of native fish and frog recovery efforts, a reliable prey base is present to support newly released northern Mexican gartersnakes.
The Las Cienegas National Conservation Area is the focus of several significant conservation programs in addition to the snake. Conservation and recovery projects for rare or federally listed species in this area have been designed and implemented on an ecosystem level, focusing on native riparian and aquatic species such as the Gila topminnow (Poeciliopsis occidentalis), Gila chub ( Gila intermedia), and the Chiricahua leopard frog ( Lithobates chiricahuensis). Over the years activities have included habitat improvement projects, non-native species removal projects, and reintroductions of these species. These projects are made possible, in part, by positive working relationships between the U.S. Fish and Wildlife Service (Service) and private landowners, livestock grazing permittees, local scientists and conservationists, the Arizona Game and Fish Department, and the U.S. Bureau of Land Management.
Through these partnerships, the Service has strengthened what has been lost or weakened in many areas in the southwestern U.S., and continues to work to restore the snake and the aquatic ecosystem it depends on.
Jeff Servoss, a fish and wildlife biologist in the Service's Arizona Ecological Services Office in Tucson, can be reached at firstname.lastname@example.org or 520-670-6144. Tom Buckley, a public affairs officer in the Service's Southwest Regional Field Office in Albuquerque, New Mexico, can be reached at email@example.com or 505-248-6455.
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