FWS finds listing of Northern Mexican Gartersnake warranted but precluded, adds it to candidate list instead
73 Fed. Reg. 71788 / Vol. 73, No. 228 / Tuesday, November 25, 2008 / Department of the Interior; Fish and Wildlife Service; 50 CFR 17; Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Northern Mexican Gartersnake (Thamnophis eques megalops) as Threatened or Endangered With Critical Habitat; Proposed Rule
SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 12-month finding on a petition to list the northern Mexican gartersnake (Thamnophis eques megalops) as threatened or endangered with critical habitat under the Endangered Species Act of 1973, as amended (Act). The petitioners provided three listing options for consideration by the Service: (1) Listing the U.S. population as a Distinct Population Segment (DPS); (2) listing Thamnophis eques megalops throughout its range in the United States and Mexico based on its rangewide status; or (3) listing Thamnophis eques megalops throughout its range in the United States and Mexico based on its status in the United States. On the basis of the best scientific and commercial information available, we find that listing the northern Mexican gartersnake as threatened or endangered throughout its range in the United States and Mexico, based on its rangewide status, is warranted under the Act, due to the present or threatened destruction, modification or curtailment of its habitat; predation; and the inadequacy of existing regulatory mechanisms. Currently, listing is precluded by higher priority actions to amend the Lists of Endangered and Threatened Wildlife and Plants. Upon publication of this 12- month petition finding, the northern Mexican gartersnake will be added to our candidate species list. We will develop a proposed rule to list the northern Mexican gartersnake as our priorities allow. Any determination on critical habitat will be made during development of the proposed rule.
The northern Mexican gartersnake ranges in color from olive to olive-brown or olive-gray with three stripes that run the length of the body, the middle of which darkens towards the tail. It may occur with other native gartersnake species and can be difficult for people without herpetological expertise to identify. The snake may reach a maximum known length of 44 inches. Within the United States, the northern Mexican gartersnake historically occurred in every county within Arizona, and limited distribution in New Mexico. According to FWS, the best available scientific and commercial data shows that the northern Mexican gartersnake has been extirpated from approximately 90 percent of its historical distribution in the United States. Photo by Jeff Servoss from FWS.
EXCERPT: Riparian and aquatic habitats that are essential for the survival of the northern Mexican gartersnake are being negatively impacted throughout the subspecies’ range. Threats including water diversions, groundwater pumping, dams, channelization, and erosionrelated effects are occurring in both the United States and Mexico that affect the amount of water within occupied northern Mexican gartersnake habitat, directly affecting its suitability for northern Mexican gartersnakes. Threats from development, roads, flood control and water diversion, improper livestock grazing, high-intensity wildfire, and undocumented immigration that alter the vegetation of occupied northern Mexican gartersnake habitat are documented throughout its range and reduce the habitat’s suitability as cover for protection from predators, as a foraging area, and as an effective thermoregulatory site. However, Rorabaugh (2008, p. 26) suggests that an increased awareness of the potential for ecotourism to provide rural economic growth is occurring in many areas provide enhanced opportunities for conservation of biologically riche cosystems in the future. Nonnative plant species, in particular shrubs (genus Tamarix) and buffelgrass, are increasing their distribution in both the United States and Mexico and adversely affect habitat suitability and availability for the northern Mexican gartersnake.
SEE ALSO: FWS Questions and Answers, gartersnake.info, and prior ESA blawg posting.