SAN FRANCISCO -- California biologists are expressing alarm over the latest invasive species to take up residence in this city: African clawed frogs, which can survive tough conditions, eat just about anything and tend to breed like crazy.

Even worse, they're kind of cute -- and thus more likely to be whisked away by children and dumped into other ponds, where they spread even more.

"They are a threat," said Dr. David Wake, an emeritus professor of integrative biology at UC-Berkeley. "They've been introduced in southern California and...they change the environment quite profoundly."

Native to the African nation of Kenya, the frogs are able to live under ice, in the ground, and in bodies of water that are nearly half saltwater. They alter ecosystems by gobbling up insects, fish, lizards and even birds that manage to fit into their large, tongueless mouths. They are also able to burrow into the ground to survive dry conditions and have been known to prey on the state's endangered red-legged frog.

The African frogs, outlawed in California as pets several years ago, are typically used in medical and biological research.

Biologists theorize that their residence in Golden Gate Park's Lily Pond and in areas of Southern California may be due to researchers depositing the frogs in the ponds to save them from destruction. Pet stores and collectors wary of being slapped with fines of up to $1,000 may have also have released them into local creeks and ponds.

Getting rid of the frogs has proved to be a problem for the California Department of Fish and Game, which has suffering from severe budget cuts in recent years.

A plan to dry out Lily Pond went awry last July just as a crew was readying pipes to flush the contents of the pond into the sewer.

"We were all set and ready to go," said Miles Young, a retired patrol lieutenant with the Department of Fish and Game who said he was confused by the sudden change. "We would have drained it in three hours. We spent weeks studying and preparing."

Susan Ellis, the department's invasive species coordinator, said budget constraints forced her department to divert funds to more threatening species on California's long list of invasive organisms, including the New Zealand mud snail and the northern pike that has taken over Lake Davis, near the Sierra community of Portola.

"We would like to get those frogs out of that pond," Ellis said. "But because of our current situation with budget cuts and personnel, it just isn't at that point. Some of the rehabilitation of the ponds has been slowed and this pond is not on the list."

But some, including Young, say the department is more worried about failure than budgets, especially in light of the bad publicity the department received following efforts to eradicate the northern pike at Lake Davis in 1997.

State wildlife officials pumped 50,000 pounds of poison into the lake in an effort to get rid of the voracious invasive fish, which threatens the lake's trout population and downstream salmon.

The effort caused an uproar among Portola residents who rely on the lake for their drinking water and for tourist dollars from vacationers. The poison stayed in the lake for weeks and killed most of the animal life -- except, for some reason, the northern pike, which still thrive there today.

Young said he believes the pike had returned to Lake Davis because fishermen threw them back in, and said the state's bad experience there shouldn't keep it from going after the African frog.

"We can't say 'we don't want another Portola so let's not do anything,"' Young said.

The Fish and Game Department's Ellis insists the frog population in Lily Pond has been contained for now. But some biologists, who say it's harder to find the frogs in deeper ponds, aren't so sure.

Eric Mills, coordinator for the Oakland-based Action for Animals, said he has been lobbying state Fish and Game departments about the frogs since last year.

"They spent millions of dollars a few years ago in San Diego trying to get rid of these frogs," Mills said. "If they get loose in the San Francisco delta, it will be devastating to get them out."