The aquatic snake, which is found in Arizona and Mexico, is now one of 282 species awaiting approval to be protected under the Endangered Species Act.
While authorities have not been able to estimate its current population numbers, the olive-colored snake with striking yellow stripes has been reduced to possibly less than 10 percent of its former distribution, according to the U.S. Fish and Wildlife Service.
Wildlife officials say the snake is important because its health is an indication of the well-being of other species and the river systems that share their habitat.
The Mexican garter snake is found in parts of the Verde River, Tonto Creek and the San Rafael Valley, but they used to be found throughout much of Arizona and in western New Mexico. They began declining in numbers as humans moved in on their territory or diverted the rivers and streams where they used to thrive.