Nature's Way
Tutorial on Turtle Trapping
by Lakin Khan
The first days of real spring, gentle-breezed, air-warm. I walked out to the ponds on just such a soft day, so welcome after the harsh rain and exceptional cold that February dropped upon us. Ducks and geese floated serenely on the pond, a cormorant or two popped up here and there before diving down again.
Across the way, two guitarists sat, plucking soft tunes that fit the gentle day. Had they looked up they might have noticed the unusual activity at the west end of the larger pond, but they carried on, providing a lyrical soundtrack to the baiting and setting of the turtle traps. That, of course, is where I was headed.
The Western Pond turtle (Clemmys marmorata) is a shy creature, our only native fresh-water turtle west of the Sierras. We are lucky to have some in our two ponds, for native turtle populations all along the coast are dropping as freshwater habitats dwindle and invasive species, such as the aggressive Red-eared Slider explode, out-compete the more laid back, groovy native. Currently, its numbers are so low, the Western Pond Turtle is listed as a Species of Federal Concern, one rather narrow rung away from Endangered.
This is why, on these first spring-like days, a professor, a grad student and a few undergrads are lurking around the pond with mesh-sided traps and cans of sardines. Becki Gordon, a master's degree candidate in biology, has selected the Western Pond Turtle as the subject of her thesis.
"I like turtles, they are so archaic; they haven't changed much since we first see them in the fossil record from the Triassic," says Gordon. Working with Dr. Nick Giest, SSU's biology professor in charge of most things amphibian, reptilian and dinosaurian, she has developed a three-part project that will examine the turtle's plight, with an aim to restoring the balance between native and invasive populations.
Catching turtles by hand is no mean feat. It doesn't take much to alert these wary critters, causing them to bolt over the concrete edge of the pond, slipping under the mat of algae and into the muck at the bottom. This is where the traps come in: mesh-sided cylinders with funnel-shaped entrances on each end, a punctured can of sardines hanging inside as bait. This is why the students are gathered for this catch-and-release turtle trapping tutorial to kick off the project. "We'll probably find 10 red-eared sliders in here for every pond turtle," predicts Geist, who secured a $2,500 RSCAP grant which, paired with a grant from the California Fish and Game Service for $6,355, will fund this Head Start Program for Western Pond turtles.
The project is structured around three tasks. First, Gordon and her undergrad assistants collect as many turtles as they can in four different locations: the two ponds on our campus, Ledson Marsh, Fairfield Osborn Preserve and some agricultural ponds in Napa.
After measuring and tagging all collected Western Pond turtles, they will outfit 25 females with radio-tracking devices so that in June and July they can be followed to their nesting sites, which can be up to a mile away from their hang-out water sites. After noting the details of the nesting locations, the team will gather turtle eggs for part two of the project: incubation.
The Western Pond Turtle has the distinction of being a TSD species, or temperature-dependent sex determination, which means that the gender of the hatchlings is determined by the temperature of the egg incubating in the nest. At this point, it is unknown what that precise temperature is. Gordon will incubate eggs at various settings to discover which gender is produced by what temperatures.
"The determining difference could be as little as a degree or two; it's a very narrow window," Geist said. The larger, nagging questions remain: How does global warming affect this process? Could variations in temperatures world-wide create a skewed ratio between male and female turtles, perhaps further undermining their reproductive success?
Part three is the pay off for the species: once the baby turtles have hatched, been sexed and the data recorded, they will be released in the fall to the watery environments most favorable to them, with desirable nesting sites nearby in high hopes of restoring the populations of these small, archaic beasts.
On this balmy spring day, though, the practice session continues. Sardine oil drips out of the cans dangling from the support rods of the four traps; it is time to get them into the water. Geist, outfitted in a one-piece brown waterproof jumpsuit and thick sneakers as protection against the murky water and the gunk on the bottom of the pond, volunteers to wade out to place the traps. As the breeze becomes a slight wind, two traps bob slightly in each pond, waiting for turtle residents.
And the next day, warmer and even more spring-like, Geist
reassembles his gear and drags the traps in, holding a
total of three turtles, two of them Western Pond turtles,
a good sign, though not statistically significant at this
point. The students practice the proper methods of holding
and measuring turtles, learn to distinguish between the
two species (easy enough close up, but difficult from a
distance), and discuss the best ways to attach the telemetry
once they arrive.
Then the turtles are released to the pond, the practice session over, to await the official start of the program. After Geist's description of what his feet might have been walking on or through, the students all agree that perhaps a small inflatable boat or kayak might be a better approach than jumpsuits and sneakers.
NOTE: Lakin Khan has been awarded an Artist’s
Grant and Residency at the Vermont Studio Center for the
month of April. The Center is located in the town
of Johnson, just outside of Burlington in the Lake Champlain
district and is highly regarded for its support of emerging
and established artists and its international program.
She will be there for two weeks, working with the esteemed
author Ron Carlson, whose latest novel; “Five Skies” is
due out in May.
E-mail our amateur campus naturalist with any observations, stories or reactions you have about our shared environment with the natural world on campus. Khan is an administrative coordinator in the biology department and can be reached at lakin.khan@sonoma.edu.