Mark Twain's 1865 tale of a frog-jumping contest draws more than 40,000 visitors each May to this historic mining community in the Sierra Nevada foothills.

But those hoping to see the star of the story may be out of luck.

The once-common California red-legged frog -- which many scientists believe to have been "The Celebrated Jumping Frog of Calaveras County" -- is gone. The animal's disappearance from the region has forced the county to recruit bullfrog jumpers, and led to debate on whether to bring the frog back.

Environmentalists and scientists have seized on the famous frog to illustrate the dangers facing one of the "indicator species" they use to gauge the health of the Sierra region.

"We have an obligation to the frog to see it into the future . . . as a tribute to Mark Twain and the frog that put us on the map," said Robert J. Stack, a genetics researcher who was so intrigued by the frog after he moved to Calaveras County that he formed the Jumping Frog Research Institute.

But local officials fear the frog's return could hurt development -- and even the contest. They also say there's no certainty that the red-legged frog is the one in Twain's narrative.

Warren "Buck" King, the unofficial "Frogtown mayor" who manages the Calaveras County Fair and Frog Jumping Jubilee, has helped lead opposition to the reintroduction for fear "it could mean the demise of the frog jump."

"The frog is what has made Calaveras County and Mark Twain famous, and it's been a good match," said King, who has been involved with the fair and jumping contest for 32 years.

He said there's no proof Twain's frog had red legs. "It was a fictitious story, and it wasn't based on a real incident." He said he suspects environmentalists are just using the frog to promote environmental protections.

As many as 2,000 frogs are set to jumping each May at the Frogtown fairgrounds. The competition echoes the first frog jumping contest the local booster club organized in 1928 to celebrate the paving of Main Street.

Today, the sidewalks of Angels Camp are lined with painted green frogs and bronze plaques modeled on the Hollywood Walk of Fame.

The world record holder, "Rosie the Ribiter," has a plaque for her 21-foot, 53/4-inch triple jump. There's a standing $5,000 prize offered for any frog that breaks the record, which has stood since 1986.

But Twain's frog has the place of honor, right outside the Angels Hotel. The hotel's bar was frequented in the autumn of 1865 by the budding journalist -- then known as Samuel Clemens -- who was living in a cabin in nearby Jackass Hill.

The bar is where he heard the tall tale he turned into a short story about a frog called Dan'l Webster, "whirling in the air like a doughnut" during one of its jumps that could "get over more ground in one straddle than any animal of his breed you ever see."

The red-legged frog was killed off in part because San Franciscans found its large legs quite tasty around the turn of last century.

Entrepreneurs imported even larger, but less delectable, bullfrogs from east of the Rockies to feed the frog leg craze. Descendants of the newcomers helped drive out the red-legged natives.

Today, scientists say competition, habitat loss, climate change, ultraviolet radiation and windblown pesticides are devastating not only the red-legged frog, but other frog species throughout the Sierra.

The U.S. Fish and Wildlife Service said the frog's historical range has shrunk 70 percent. Though the frogs still can be found in 256 drainages, most are in enclaves along the north-central coast. The Center for Biological Diversity says there are now only four places known to have populations greater than 350.

"There's quite a few along the coastal areas, and I say, 'Well, Mother Nature made a decision,' " King said. "Why introduce them here when they might not do so well? They should just let Mother Nature move the frog, not Fish and Game."

Stack, who has been involved in lawsuits to protect the frog, said he hopes schoolchildren might someday raise the frogs and release them into ponds as part of a voluntary arrangement to protect Sierra foothill range lands.

The bullfrogs would have to be removed or killed wherever the red-legged frog is reintroduced. But controlling bullfrogs in a particular pond could be as simple as letting the pond go dry every few years -- something red-legged frogs can survive, but bullfrogs cannot.

Stack said the red-legged frog can be reintroduced by eradicating the bullfrog from only a few ponds, and that reintroducing the red-legged frog would be a publicity boon for the county and the contest.

"The bullfrog is the frog of the frog-jump, no doubt about it," said Stack. "I think the most wonderful thing in the world would be to have the red-legged frog challenge the bullfrog in a grudge match."

Buck King, manager of the Calaveras County Fair and Frog Jumping Jubilee, opposes reintroducing the California red-legged frog, as some have favored.On Main Street in Angels Camp, Calif., a plaque commemorates each

winner of the frog-jumping contest.