The Fossil Turtles of Hagerman: Just Shells of Their Former Selves
Idaho is not known for its turtles. In fact, many people may not be aware that there is even a turtle living in the state, the painted turtle, found only in the panhandle. Since there are no turtles living in any parts of the Snake River drainage today, it may be somewhat of a surprise to learn that pieces of turtle shell are one of the most common fossils found at Hagerman Fossil Beds and that two types of extinct fossil turtles have been found here.
The second type of turtle found as a fossil at Hagerman is an extinct species of the Western Pond Turtle, Clemmys owyheensis. The living species of Clemmys, C. marmorata, lives along the Pacific Coast from southwestern British Colombia to northern Baja California with an eastern population in the Truckee and Carson Rivers of Nevada. The presence of the Nevada population between Hagerman and California is further evidence for the former drainage of the Snake River out of Lake Idaho across northern Nevada and into northern California.
The living species of both Trachemys and Clemmys are thoroughly aquatic turtles that seldom venture on land. That their close relatives are common as fossils at Hagerman fits our interpretation, suggested by many of the other animals such as beaver, muskrat, otter, frogs and the waterfowl, that 3.5 million years ago an extensive wetland habitat existed in the area. Their disappearance from southern Idaho probably resulted from the increasing drying and cooling of the region and loss of suitable habitat, possibly caused by the continued uplift of the Cascade Mountains and the resulting rain shadow in Idaho. Although not present in Idaho today, studies of their surviving descendants in other areas can provide us with an insight into what the environment was like in southern Idaho 3.5 million years ago.