Non-Native Species|Threaten Gartersnake

     WASHINGTON (CN) – Due to drastic population declines, the northern Mexican gartersnake and the narrow-headed gartersnake were listed as threatened under the Endangered Species Act (ESA), Tuesday.
     The listing designations were spurred by a 2011 court settlement between the U.S. Fish and Wildlife Service and the Center for Biological Diversity (CBD). The settlement created a five-year work plan for the USFWS, designed to speed listing determinations for hundreds of species across the country. The CBD petitioned for the Mexican gartersnake’s protection in 2003, and submitted a status report to the USFWS documenting the narrow-headed garter’s need for protections in 2011, according to the CBD’s response to the listing.
     “The snakes have undergone dramatic, range-wide declines in the United States and are now almost entirely limited to small, isolated populations at risk of extirpation,” the group said. Extirpation refers to the localized extinction of a species from a particular area.
     The USFWS’ press release noted that 83 percent of the U.S. populations of northern Mexican gartersnakes and 76 percent of narrow-headed populations have low viability and may have such low population densities that they could be, or perhaps already are, wiped out. Data from field research in Mexico indicate similar trends in northern Mexican gartersnake populations in that country.
     The agency maintains that the primary threat to gartersnake populations comes from the introduction of nonnative species such as bullfrogs, crayfish, warm-water predatory sportfish, and brown trout. “These harmful nonnative species prey upon, or compete with the gartersnakes and the native prey species (including native amphibians and fish) that are vital to their existence,” the agency said. Other threats, such as large-scale wildfires and water degradation are also significant, but especially so in combination with the pressures from nonnative species, according to the agency.
     “The decline of these snakes is typical of the catastrophic loss of aquatic animals across the Southwest,” CBD attorney Adkins Giese was quoted as saying in the group’s response. “These snakes depend on native fish and amphibians for their food, and the widespread loss of the snakes and their prey reflects a severe collapse of the food web in southwestern rivers and streams.”
     The threatened listing status allows the USFWS to invoke a special rule under Section 4(d) of the ESA to exempt livestock tanks from prohibitions on harming listed species during normal use of the tanks. The special rule, which is not allowed for species designated as endangered, exempts landowners from the prohibitions on “take,” or harm, to the snakes in connection with normal operation or maintenance of livestock tanks on private, state or tribal lands.
     “Some northern Mexican gartersnakes occupy stock tanks, or impoundments maintained by cattlemen as livestock watering holes. The special rule will allow landowners to construct new stock tanks and to continue to use and maintain those stock tanks on non-federal lands, which may be occupied by northern Mexican gartersnakes, without the need for further regulation,” the agency said.
     The agency plans to issue a critical habitat designation at a later time.
     The listing is effective Aug. 7.

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