Turtles Return to Yosemite Ponds After Bullfrog Removal
Scientists found juvenile northwestern pond turtles again after nearly eradicating invasive American bullfrogs from two Yosemite ponds by 2019.
Updated on Nov. 6, 2026 in National Parks
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Between 2016 and 2019, scientists removed 16,384 bullfrogs, larvae, and egg masses from two Yosemite National Park ponds, and by 2019 juvenile northwestern pond turtles had reappeared there. The seven-year monitoring study of four turtle ponds concluded in 2022.
Why it matters
Northwestern pond turtles, one of California's two native freshwater turtle species, have lost more than half of their historical range. Newly hatched turtles are small enough to fit into a bullfrog's mouth, and bullfrogs prey on young turtles along with other wildlife.
Turtles were 2 to 100 times more common at Yosemite ponds without bullfrogs than at ponds with them, and turtles found alongside bullfrogs were 26 to 36 percent smaller and 76 to 97 percent lighter. The study's long-term sustainability of the recovery was not addressed.
The players
Yosemite National Park
A protected national park in California's Sierra Nevada known for its granite cliffs, waterfalls, and diverse ecosystems.
The details
Scientists removed 12,317 bullfrogs, larvae, and egg masses from one site and 4,067 from another, gradually reducing the invasive population until it was almost eradicated by 2019. Juvenile turtles of all age classes were observed at ponds without bullfrogs.
Timeline
2016: Monitoring of four Yosemite turtle ponds began.
2019: Bullfrogs were nearly eradicated and juvenile turtles reappeared at ponds.
2022: The seven-year monitoring study concluded.
Big Picture
The American bullfrog, introduced to the western United States in the twentieth century, became established in Yosemite in the 1950s and had spread to several parts of the park by the mid-1970s. This Yosemite turtle recovery reverses a decades-long period in which that introduction contributed to the decline of native turtles.
Visitors to Yosemite can observe the park's ponds and wildlife, but the study does not establish specific visitor guidance. Travelers interested in the park's natural areas should check current park conditions before planning trips.
The takeaway
Removing an invasive predator can allow a native species to return to habitat it had lost, as the Yosemite pond turtles show. Long-term monitoring helps determine whether that recovery lasts.
Further reading
For more on protected landscapes, explore National Parks coverage across California.
Source note: This article includes information reported by Economic Times.
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