Point Reyes Light - April 29, 2004
A threat to native western pond turtles
By Ivan Gale
The western pond turtle, a native species which has long suffered from the loss of its natural habitat, is now finding itself being crowded out by introduced, exotic turtles which have descended from unwanted pets.
Separately, the Marin Municipal Water District and the Salmon Protection and Watershed Network this week announced actions they have taken to prevent the demise of the western pond turtle in local waterways.
Pets released in wild
Marin Municipal has begun a two-month-long project to trap an introduced species of turtle called a "red-eared slider" at Lagunitas, Alpine, and Phoenix reservoirs. Once caught, the turtles will be given to a turtle adoption program in Clovis, Fresno County.
Red-eared sliders are commonly sold at pet stores. Because of easy access to Marin Municipal’s reservoirs, it is believed the waterbodies have become targets for illegal dumping of turtles and non-native fish such as largemouth bass, bluegill, sunfish, as well as amphibians like bullfrogs.
In Phoenix Reservoir near Ross, where aquatic ecologist Eric Ettlinger is beginning his trapping project, more than 100 exotic slider turtles are thought to exist, while the native pond turtle population is likely down to under 10, according to Ettlinger. Out of those remaining native turtles, only one female has been identified.
"Our reservoirs are some of the best habitat left [for western pond turtles]," Ettlinger told The Light Tuesday. "As they lose habitat here, it becomes more likely we’ll lose them throughout Marin County."
SPAWN saves turtles too
Meanwhile SPAWN biologists have announced a separate turtle species has been found in a creek in the Lagunitas watershed. A nine-inch spiny softshell turtle, native to the Midwest and also sold in pet stores, was first spotted by naturalist David Ford during a spawning survey.
"I saw a tiny snout sticking out from the sediment on the creek bottom so I dug down, and to my surprise, pulled up this turtle," Ford said.
Although only one such turtle has been discovered in local creeks, SPAWN biologist Todd Steiner warns the threat these introduced turtles pose to coho salmon is significant.
"Spiny softshell turtles are fish predators and this turtle may have been feeding on juvenile salmon and steelhead," Steiner said. "Furthermore, the introduction of non-natives into our streams always runs the risk of introducing new diseases that could impact a multitude of native species."
It is the threat of passing along diseases, ironically, that is one reason why turtles are released in the first place.
Ecologist Ettlinger said when baby red-eared sliders are first bought in pet stores, their red markings and yellow stripes are bright.
"Sliders are beautiful when little, but then they can grow too large for a 10-gallon aquarium," Ettlinger said, adding that as adults they lose their attractive markings, they begin to bite, and they start to smell bad.
"When people learn turtles can make children sick from salmonella," he said, "they release them."
Catching a turtle
To entice them into funnel shaped traps, Ettlinger lures the turtles with strips of beef. Turtles are omnivorous scavengers, preying on injured fish as well as pond plants. When they are young, they rely on eating meat to give them protein to grow. As they grow older they gradually switch to a more vegetarian diet.
While western pond turtle numbers are dangerously low in Phoenix Lake, the population fares better in less-accessible reservoirs such as Lagunitas Reservoir. In fact, the largest western pond turtle in the world was found there last summer, at a length of eight-and-three-quarter inches.
To help restore the native turtle in Phoenix Reservoir, Ettlinger said he is considering relocating some of the native turtles from Lagunitas Reservoir.