Bullfrogs look forward to this time of year the way some locals anticipate Hood strawberry season. It's the time when baby western pond turtles in the Columbia River Gorge emerge from months of dormancy and begin swimming about — making an ideal "fun size" snack for the voracious, non-native American bullfrog.
"When you're as small as these guys are, you're the perfect size for a lot of animals to eat," said Oregon Zoo keeper Michelle Schireman. "And the biggest problem they have right now are the invasive, or introduced, bullfrogs — they just scoop them up like M&M's."
Native to the eastern United States — but considered an invasive species here — the American bullfrog is the largest frog species on the continent. It can tip the scales at more than a pound and has been driving pond turtles and a host of other small, vulnerable aquatic species to the brink of extinction.
Last week, Schireman and her colleagues took charge of 20 western pond turtle hatchlings, collected by the Washington Fish and Wildlife Service from sites in the Columbia Gorge. The zoo is "head-starting" these tiny turtles, caring for them until next spring when they will be large enough to avoid the bullfrogs and have a fighting chance on their own in the wild.
Unlike recovery programs for other endangered species like California condors or Taylor's checkerspot butterflies — which take place offsite or behind the scenes — this conservation effort can be seen by zoo visitors. The turtle conservation lab is in the Cascade Stream and Pond portion of the zoo's Great Northwest section.
The turtles experience summer year-round, with heat lamps and plentiful food, so they don't go into dormancy. "Life's pretty easy here in the lab if you're a little pond turtle," Schireman said. "As a result, they grow to about the size of a 3-year-old during the nine months that they stay with us."
Once the turtles reach about 70 grams (a little more than 2 ounces), they are returned to their natural habitat and monitored for safety.
The western pond turtle, once common from Baja California to the Puget Sound, is listed as an endangered species in Washington and a sensitive species in Oregon. The species is currently under USFW review to determine whether it will be given federal protection under the Endangered Species Act. Two decades ago, western pond turtles were on the verge of completely dying out in Washington, with fewer than 100 turtles left in the state.
"We're at a critical point with this species," Schireman said. "We really have to grow them up in their population numbers if we're going to save them in time."
There have been some encouraging signs. In one study, scientists estimated that 95 percent of turtles released back to sites in the Columbia Gorge survive annually, and today nearly 1,000 turtles range across six ponds in the Columbia Gorge.
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