The frog featured in Mark Twain's famous short story, "The Celebrated Jumping Frog of Calaveras County,"was probably a California red-legged frog. When the tale was published in 1865, the red-legged frog was the most widespread amphibian in the state. But even then it was beginning to suffer from the ills that can send a species into a downward spiral—overhunting, changes in habitat, and the introduction of nonnative species.

Frog legs were considered a delicacy even in the nineteenth century; as a result, the frog was hunted for food. In addition, the frog's habitat was dwindling.The California gold rush of 1849 had brought miners to the state.Their excavations allowed streams to fill in with silt and dirt, reducing the clean-running water where the frogs thrived. Finally, at the end of the century, as red-legged frogs became hard to find, someone introduced...