The U.S. Fish and Wildlife Service announced today that adding the northern Mexican gartersnake, a subspecies found in the southwestern United States and in Mexico, to the list of species protected under the Endangered Species Act is warranted but precluded by other higher listing priorities. The finding will be published in the Federal Register tomorrow.
On January 4, 2006, we published a 90-day finding that a petition, from the Center for Biological Diversity to list the northern Mexican gartersnake as threatened or endangered presented substantial scientific information. On September 26, 2006, we published a 12-month finding that listing the northern Mexican gartersnake was "not warranted," citing a lack of information on the species status and threats in Mexico. However, s ince 2006, new information on threats to this species in Mexico has been identified and further declines of the species have been documented in Arizona. Within the United States, the northern Mexican gartersnake has been reduced to possibly less than 10 percent of its former distribution.
The northern Mexican gartersnake will be classified as a candidate species until a proposed rule can be prepared.
"The northern Mexican gartersnake faces significant threats in the United States and Mexico; however, we dont have the resources at this time to engage in the listing process for all species nationally that warrant Endangered Species Act protection," said Steve Spangle, Arizona Field Supervisor.
Northern Mexican gartersnake populations in Arizona, New Mexico, and Mexico have declined primarily from interactions with nonnative bullfrogs, crayfish, and nonnative fish that prey upon, or compete with, the northern Mexican gartersnake and its native prey species. Human activities that result in the reduction, elimination, or degradation of surface water or vegetation are also significant threats, but particularly where they co-occur in the presence of nonnative species. Efforts to control nonnative predators and restore native aquatic and riparian riparian
Definition of riparian habitat or riparian areas.
Learn more about riparian communities could significantly benefit northern Mexican gartersnakes and a suite of other imperiled native fish and amphibian species throughout its range.
The northern Mexican gartersnake can grow to 44 inches, is olive colored and has three stripes that run the length of the body with a yellow stripe down the back that darkens toward the tail. A light-colored crescent extends behind the corners of its mouth. Northern Mexican gartersnakes are difficult to distinguish from other native striped gartersnake species in Arizona. Northern Mexican gartersnakes live in dense vegetation along the banks or in the shallows of wetlands (cienegas and stock tanks) and within pool or backwater habitats within streams. In the United States, northern Mexican gartersnakes occurred at elevations ranging from 130 to 6,150 feet. In Mexico, they have been found at elevations as high as 8,497 feet. They feed primarily in or near water on native fish and frogs and less commonly on earthworms, lizards and small rodents on land.
Historically, the snake lived in perennial rivers, intermittent streams and isolated wetlands throughout the southern half of Arizona, extreme western New Mexico, and the Sierra Madre Occidental and Mexican Plateau in Mexico which collectively represents approximately 70 to 80 percent of its historical distribution. The last observation of this species in New Mexico was in 2002. Mexican scientists have documented the expansion of the exotic American bullfrog in Mexico, a particularly serious threat to the gartersnake and its prey base.
The current distribution of the northern Mexican gartersnake within the United States is believed to be constrained to the middle/upper Verde River drainage, middle/lower Tonto Creek, the San Rafael Valley, as well as in a small number of isolated wetland habitats and stream reaches in southeastern Arizona. The subspecies is listed as threatened throughout Mexico by the Mexican government.
Information regarding northern Mexican gartersnake status or its habitat should continue to be submitted to the Field Supervisor, Arizona Ecological Services Office, 2321 West Royal Palm Road, Suite 103, Phoenix, Arizona 85021-4951.
