Barely bigger than an English muffin, the dark-shelled turtle flails his webbed feet, and cranes his neck to peer at the people carefully applying epoxy to his shell. Usually a reclusive conservation celebrity, this pint-sized reptile is one of five turtles being released into a San Diego watershed to bolster wild populations of California’s only native freshwater turtle species. For western pond turtles (aka Pacific pond turtles) Emys marmorata the team of federal, state, and zoo scientists releasing the juvenile turtles into the Sycuan Peak Ecological Reserve is a much-needed effort to prevent their extinction.
Three years of collaboration between the U.S. Geological Survey (USGS), California Department of Fish and Wildlife, San Diego Association of Governments, and the San Diego Zoo are invested into this pilot project to “headstart” pond turtle youngsters and remove nonnative species from their habitat. “We have raised these turtles at the Zoo to get them large enough to avoid predation after release,” explained Thomas Owens, San Diego Zoo senior keeper. “It’s been like reverse quarantine for them. They are isolated from animals in the collection and we make sure they are handled according to protocol to ensure we will not transmit any diseases to wild populations when we release them.” With a three- and four-year “headstart,” the juveniles are no longer bite-sized morsels for other animals.
Two days before the release, staff gathered at the Reptile House at the Zoo to test and attach the radio transmitters. Clean and dry (unusual for a turtle), each turtle was weighed before the three-gram “radio pack” was attached and then weighed after it was attached. The rule of thumb is that radio packs or GPS devices should not exceed five percent of the animal’s body weight. “Large species like elephants and crocodiles, among others, have been tracked using GPS devices,” said Thomas. “But with these small turtles, which only weigh about 300 grams, it’s necessary to use tiny battery-operated devices like these radio packs. These weigh one to two percent of the turtle’s body weight.” The battery will last about three months.
The antenna is carefully glued to the turtle’s scutes to not interfere with its shell growth. After much measuring and trimming of the wire, it was carefully held in place until the epoxy hardened. The first four turtles stayed safely tucked inside their shells throughout the procedure, but the last one was more rambunctious and dared to look around, urinate, and squirm in the scientist’s grasp. “The turtles all have their own personality,” said Thomas. “Some are shy and some are more assertive.” That also explains the significant size difference between them: the oldest is not the biggest, but rather a more aggressive feeder. When they hatch, the pond turtles are about the size of a quarter, so they can be easily predated by a variety of other animals. Now, at three and four years old, these guys are past the appetizer size and appear robust and healthy; they won’t go down without a fight.
We met up with Thomas and two other reptile keepers, Rachel and Brandon. The five pond turtles were secured in a box with a wet towel, ready for their journey to East County. After close to an hour’s drive, the road turned dusty and wound through rustic riparian forest dotted with car-sized boulders: we entered the Sycuan Peak Ecological Reserve. Staff from our partner organizations joined us at the gate to the reserve. Another short drive and a short hike landed us at a pool with all the things a pond turtle loves: logs and granite rocks for basking, fresh, cool water for swimming, cattails and willows for shade, and plenty of insects and invertebrates to eat. Placed gently on the water’s edge, each turtle swam swiftly into the murky pond to begin its life anew.
The released turtles will be checked on daily by USGS and Zoo staff will radio track them three times a week. “Once they have established their mircrohabitat, they won’t have to be monitored so frequently,” said Thomas. Shortly before the transmitter batteries run down, scientists will catch the turtles again, give them an exam, and attach a fresh radio pack. Nonnative predators like bullfrogs and sunfish have been removed from the area to improve the turtles’ survival. “It’s exciting to partner with organizations to help restore native species to local watersheds,” said Thomas. For the mysterious western pond turtles, the project is going swimmingly!
Karyl Carmignani is a staff writer for San Diego Zoo Global.