Foreign Frogs Frighten San Fran

(CBS)  By all appearances it is a tranquil haven, reports CBS News Correspondent John Blackstone.

But lurking just beneath the calm surface of the lily pond in San Francisco's Golden Gate Park is a feared foreign amphibian: the African Clawed Frog.

The African Clawed Frog is kept as a pet in some states but it is banned in California because it competes with and consumes native species.

"They are really hard to pick up because they're very slippery," said Ken Howell, Asst. Curator, California Academy of Sciences. "And if you look at the back you and see the claws -- the three claws on the back there."

Nobody knows how the outlawed amphibians got into the lily pond but they have reproduced wildly threatening to wipe out most everything else.

"These are very aggressive and invasive frogs - they will eat anything they can get their mouth around," said Eric Mills, with Action for Animals.

A plan to kill or capture the frogs by draining the pond was cancelled by the California Department of Fish and Game. Some call that a foul up -- it's fueling fears the forbidden frogs could flourish far and wide.

But officials say they are still looking for a way to wipe out a creature that after millions of years of evolution is almost indestructible.

"You can't poison these frogs. You can't blow them up. There's no way to get rid of them,'' says Rob Floerke, Regional Manager of the California Department of Fish and Game.

"It extremely difficult," said Floerke. "And then, if you left two, you would be back in the same place again."

So the interlopers of the lily pond won't be gone anytime soon. When it comes to survival, these frogs have legs.