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Wednesday, June 05, 2013

Alien Invaders Wreak Havoc in Critical Habitat for Native Amphibians

• Newts and Frogs Need Protection from Aggressive Advance of Invasive Crayfish Species Introduced as Bait


They’re fast, aggressive, have ferocious pincers and powerful tails, and just like their fictional sci-fi movie monster counterparts, these alien invaders are running amok and wreaking havoc on defenseless populations.
Procambarus clarkii, the red swamp crayfish, is taking over streams and pools in the Santa Monica Mountains, and killing off native amphibians.
Lee Kats, Pepperdine University Professor of Biology, Vice Provost For Research and Strategic Initiatives, Associate Dean for Research and Frank R. Seaver Chair of Natural Science, has studied the local California newt population for 20 years and has found that invaders like the crayfish are currently the biggest threat to this species of special concern.
“Crayfish have cleared the newts out of Malibu Creek,” Kats told the Malibu Surfside News. “When the amphibians are gone, the insects are gone, too. The crayfish gobble them all up.”
“Trancas near and dear to my heart,” Kats said. He explained that the pristine canyon, which has been a National Park Service priority for acquisition and conservation, remains prime habitat for native amphibians-newts, California tree frogs and western pond turtles, with only one major threat: crayfish that have escaped from fish ponds at the golf course located up stream.
“The golf course is the source of most crayfish in the Trancas watershed,” Kats said. He explained that the ponds were stocked years ago with bluegill and bass, and that crawfish, used as live bait, have colonized the ponds and escaped into the stream.
“For years I attempted to contact the owners of the golf course, with no response,” he said. “Recently, the new owners contacted me. They are committed to draining the ponds.”
The new owners have also invited Kats and his students to survey and remove the invaders from the pools.
“We freeze them,” Kats said. The crustaceans are then donated to local wildlife rehabilitation facilities, where they are used as food for recovering animals.
Kats has four students currently working on the newt and crayfish study. Data collected over the past 14 years reveals a correlation between rainfall totals and newt numbers.
Kats explained that crayfish thrive and newt eggs vanish during years with low rainfall and that newt populations rise and crayfish decline during wet winters.
The crayfish, which need still or slow-moving water are washed away during rainy years, leaving native amphibians an opportunity to successfully breed.
Kats moved to Los Angeles more than 20 years ago and was introduced to the charismatic and rare local species of newt by a friend. “He took me to Cold Creek. I saw the newts there and said, that's it, my students and I are going to study newts.”
Kats found that he had the field largely to himself. “It blows my mind that an animal in a populated area is so little studied,” he said.
Kats has been gathering research on the newt population in the Santa Monica Mountains for 20 years and has made some astonishing discoveries. Some specimens tagged as much as 14 years ago as part of the research project, are still alive and well, returning to local streams to breed each year.
“Egg masses are the best indicator of newt activity,” Kats told The News. “Egg masses stay in place for six-seven weeks, so its easy to find them.”
“They are extremely long lived,” Kats said. “They live a long time, and have been around for a long time unchanged.”
Scientists speculate that the California newt rode the Pacific tectonic plate north from South America over the course of millions of years. The Santa Monica Mountains population are like living fossils that survive in an increasingly smaller and smaller range and may now be living on borrowed time if invasive species like the crayfish continue to expand unchecked.
“The same individual newts return each year to breed,” Kats said. “The longevity of the newt is helping it to hang on.”
Kats says it is an increasingly fragile balance. Campaigning to ban crayfish as live bait in California is one course of action that can help newts and other native amphibians. Volunteering to help remove the crustaceans from local streams is another way residents can help. Although special permits are required to remove even invasive species from waterways on public lands.
Malibu residents who have streams on their property can keep an eye out for the alien invaders and also make sure that they do not inadvertently contribute to the newts’ decline by releasing other non-native species, like mosquito fish, into Malibu’s creeks and streams.
“It’s all about making the mountains better,” Kats said. “The more we think about this part of the ecosystem, the more we know, the better it is.”

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