Tromp a few hundred feet into the Santa Monica Mountains and you will witness a rebirth: The California newts are thriving again, say biologists, because their nonnative predators, the crayfish, have vanished.
The cause of this phenomenon, like so many other quirks of nature this season, is El Nino, which filled local streams with rainwater, sweeping the crayfish into the ocean.
The crayfish, descended from ancestors brought in from Southeastern states to be sold by local bait shops, were set free in local streams by fishermen. Until this year, the clawed crustaceans attacked newts with impunity--eating the amphibians’ eggs and larvae before they could grow legs to run away.
But dozens of the small translucent newt larvae could be seen recently in Trancas Creek in Malibu, grazing on green algae.
Scientists say newts aren’t the only amphibians staging a comeback because of El Nino. The Pacific and California tree frogs--both once on their way to the federal endangered species lists--are now roaring back. So is the two-striped garter snake, a nonpoisonous reptile, also threatened by the crayfish, which grow as large as a man’s hand.
“I’ve only seen one crayfish this year, and it was dying,” says Lee Kats, Southern California’s leading stream ecologist, who would like to drive out the invaders to save local species. “My goal was to just smash the smithereens out of that sucker. But it hid in a crack--I was pretty frustrated that I couldn’t get him.”
Swollen streams quickened by El Nino-driven rains have swept the armored crawlers out to sea and have given local biodiversity a chance to flourish.
The scene was different last year, Kats says. “It looked like a bomb went off in here. The stream was thick with algae and virtually no biodiversity.”
Without the usual amphibian larvae to eat the vegetation, the stream became clogged and sluggish--perfect habitat for crayfish, but a horrible home for almost everything else. Eventually, the oxygen content of the water increased, Kats says, making it even less hospitable for young reptiles and amphibians.
Sloshing around in the boulder-studded creek, Kats everywhere sees signs of amphibian life and other encouraging signs of biodiversity. Insects known as backswimmers dart belly up through the water. Water striders skip across the rippling surface. Insect exoskeletons cling to rocks where damsel-flies metamorphosed and flew into the air.
Finally, a reason to thank El Nino.
“The newts crawled out on land and the crayfish were swept downstream,” said David Wake, director of the Museum of Vertebrate Zoology at UC Berkeley. “Our native species have evolved in our erratic weather patterns--invaders are less able to cope with that.”
But Wake and Kats agree the trials of the California newts are far from over. Although they may spawn in relative tranquillity this year and maybe next, their enemies will be back. Crayfish, like roaches, are born survivors. The hearty scavengers are adaptable, quick and prolific. And bait shops still sell them.
“I personally think the newt population in that stream is doomed in the long term,” Kats says. “It’s just a matter of whether they will go extinct in 20 years or 10 years.”
Local herpetologists say once crayfish have been introduced into a stream, it’s virtually impossible to purge them. So the only way to save the newts in Southern California is to ban their use as bait in local streams, Kats says.
California Department of Fish and Game officials say releasing such nonnative predators into the wild is already illegal, but is done all the time.
“For the most part, nobody has time to work on non-game species,” said Betsy Bolster, the department’s sole amphibian and reptile researcher. “We don’t get staffing money out of the general fund and most of our positions are for hunting and fishing enforcement.”
Local officials of the U.S. National Park Service say they plan to hunt crayfish in Santa Monica Mountain streams and finish the job El Nino started. But Ray Sauvajot, the service’s senior ecologist, acknowledges that success is unlikely.
Crayfish are not amphibians’ only threat.
Newts face dangers ranging from wildfires, which burn shade that protects delicate amphibian eggs, to mosquito fish distributed to residents by the tens of thousands by Greater Los Angeles Vector Control as an effective tool to reduce the number of mosquitoes by eating their water-borne larvae. But mosquito fish also eat amphibian larvae.
Recent studies also contend that ozone depletion and tree-devouring wildfires have torn away the blanket of shade that once protected fragile amphibian eggs from harmful ultraviolet rays.
“This is an issue that’s really bigger than us,” Sauvajot says.
Herpetologists say amphibians are dying out globally, and there is increasing evidence that California is ground zero in a national amphibian decline.
“In the Sierra Nevadas, there’s been a 90% decline in frog populations,” said Wake, one of the world’s foremost amphibian researchers. “The frog population in Yosemite and Kings Canyon has collapsed--there is probably a 50% to 80% loss of frogs in Yosemite. In Sequoia there are four major drainage systems completely devoid of frogs.”
Although the cause of these declines is still an issue of intense debate, many scientists blame pesticides or parasites in the Central Valley.
This month, Andrew Blaustein, a biologist at Oregon State University, discovered mutated frogs--once thought to be restricted to Midwestern regions--in the Willamette mountains of Oregon. “We have populations where 65% of our tree frogs have multiple legs,” Blaustein said. “We’re talking five, six, seven legs and more.”
The plight of amphibians has become so grave that U.S. Secretary of the Interior Bruce Babbitt this month formed the Task Force on Amphibian Declines and Deformities (TADD) to investigate the problem.
“Frogs may be the canary in the mine for humans,” said William Y. Brown, TADD chairman and Babbitt’s science advisor, referring to the old practice of miners carrying a canary, which would alert the miners to danger by passing out from exposure to small amounts of otherwise undetectable poison gas.
“Frogs and toads have been around since the Jurassic period--I’ve always imagined them squatting in the footprints of Tyrannosaurus rex. They’ve been around a lot longer than humans have, so we should pay attention to this dramatic evidence of declines.”