Restoring balance: Recovering the northwestern pond turtle and northern leopard frog
Washington’s wetlands are home to a wide diversity of wildlife, including everything from aquatic invertebrates to amphibians and migratory birds. Two of Washington’s iconic wetland species, the northwestern pond turtle and the northern leopard frog, are listed as endangered in the state. In the face of habitat loss, invasive species predation, disease, and population isolation, Washington Department of Fish and Wildlife (WDFW) and many partners have been working to help recover these species.
Biologists like WDFW’s Patricia Valcarcel are helping lead the charge toward recovery for the northwestern pond turtle and northern leopard frog.
“Both species are unique in terms of their habitats and their locations,” said Valcarcel, a herpetologist focused on the recovery of endangered and threatened reptiles and amphibians. “In Washington, the northwestern pond turtle is at the northern edge of its range, while the northern leopard frog is at the very western edge of its range.”
Once found in several regions across Washington, these species have seen their habitats shrink dramatically or disappear entirely. Northern leopard frogs were historically scattered across floodplains in Eastern Washington, including wetland areas along the Pend Oreille, Columbia, and Walla Walla rivers. Today, there is only one wild population remaining in the state.
Historic populations of northwestern pond turtles were concentrated in the Columbia River Gorge and Puget lowlands. Recovery efforts have increased Washington pond turtle populations from two to six, with about 800 individual turtles across the state. Still, many roadblocks to pond turtle recovery remain, including invasive species and a fungal-associated shell disease.
Biologists consider the northwestern pond turtle and northern leopard frog “indicator species.” Their presence, or absence, acts as a barometer of the overall health of the wetland ecosystems that they call home; ecosystems that are biodiversity hotspots for other Washington wildlife.
Habitat loss is largely to blame for these species’ declines. Floodplain development and wetland disruption have heavily impacted northern leopard frogs, while urbanization and the conversion of prairies and wetlands for agriculture and development have impacted northwestern pond turtle populations.
“Habitat modification and loss was the original reason for their decline,” Valcarcel said. “But as we work toward recovery, we’re now dealing with newer threats, like invasive species that prey on our native populations.”
One Washington invasive species in particular poses an enormous threat to both northern leopard frogs and northwestern pond turtles: the American bullfrog. A non-native, introduced species in the western United States, bullfrogs are prolific breeders and highly opportunistic predators.
“Bullfrogs are a major threat,” Valcarcel said. “They’ll eat adult [northern leopard] frogs, metamorphs, and anything else that goes in front of their mouths. They can outcompete native species by sheer numbers and their predatory nature.”
While adult northwestern pond turtles grow to be much bigger than bullfrogs, hatchlings are only about the size of a quarter and will remain vulnerable to bullfrogs for up to three years. So, when biologists find bullfrogs in ponds with northwestern pond turtle hatchlings — that means trouble, according to Valcarcel.
“Bullfrogs can reduce the number of hatchling and juvenile turtles reaching reproductive age in a population,” she said. “You need enough juveniles reaching adulthood and reproducing to develop a self-sustaining population, so hatchling and juvenile predation by bullfrogs is a real problem.”
This dynamic has made habitat restoration efforts increasingly complex. Recovery teams have to factor in strategies to manage invasive species while ensuring that restored habitats meet the needs of native wildlife.
Despite these challenges, WDFW’s recovery efforts are making headway. For northern leopard frogs, WDFW is focused on creating additional populations through headstarting and reintroduction efforts.
“Headstarting” refers to one process experts use to intervene during the early, extra-vulnerable stages of a species’ life cycle, in order to improve the species’ chance of survival. In the case of northern leopard frogs WDFW biologists collect northern leopard frog egg masses from the wild population and bring those egg masses to partners, who raise them up through metamorphosis — from a larval stage to a fully developed frog.
At that point, biologists care for the frogs in captivity for about a month, then release them first into acclimation enclosures at the recovery site for three to seven days. Once they’re acclimated to their new habitat, WDFW releases the frogs fully into the recovery site in the wild. Raising these juveniles in captivity gives them a “head start” and better chance of survival once they’re released into the wild. This strategy aims to bolster genetic diversity and establish new strongholds for the species.
“Right now, we have one isolated northern leopard frog population in Eastern Washington which is highly dependent on the water management in that area. Our goal is to increase resiliency and establish additional populations,” says Valcarcel.
For the northwestern pond turtle, efforts have revolved around habitat restoration combined with headstarting programs to get hatchlings growing into captive-reared juveniles that, once released back into the wild, are big enough to withstand bullfrogs and old enough to reproduce on their own.
“When they’re raised in captivity, they grow a little bit faster and have a bit of a ‘head start,’” says Valcarcel. “At one year, they’re at an appropriate size to release back into the wild, whereas it might take three years for them in the wild to grow to that same size. And that size threshold is what we’re looking for to get them big enough to avoid bullfrog predation.”
For WDFW Assistant District Biologist Emily Butler, who has helped implement pond turtle recovery projects in Pierce County, the needle is moving in the right direction toward recovery.
“We’ve definitely seen success,” she said. “We track released turtle survival and growth progress, and also put transmitters on breeding-size females to help lead us to new nests each year.”
Headstarted turtles aren’t the only ones making progress, thanks to ongoing habitat restoration efforts. “We’ve started to catch turtles every year that were born in their natural habitat and survived fully in the wild on their own,” says Butler.
“In 2024, we actually caught a wild turtle that was seven years old and had evaded capture so far,” Butler said. “It was nice, big, and healthy. That was really exciting and shows that good things are in the habitat that can support natural reproduction.”
Two things are resoundingly clear for both endangered species recovery efforts: invasive species management can make a huge difference, and strong partner collaboration is critical.
There are several zoos that help WDFW with headstarting efforts, including Northwest Trek, Oregon Zoo, and the Woodland Park Zoo. These partners help raise headstarted frogs or turtles in captivity until WDFW is ready to release them. Along with these partner organizations, there is also a large network of researchers helping WDFW with northwestern pond turtle shell disease research.
Shell disease has emerged as a major concern for pond turtles, and WDFW and partners like PAWS, the University of Illinois, and the Oregon Zoo have worked to increase research, detection methods, and treatments for turtles with the disease.
WDFW recently awarded Wildlife Diversity Grant Program funding to multiple grantees to benefit the northwestern pond turtle, including bullfrog control efforts, expanded research on shell disease, and tracking turtle movements and habitat selection, all of which are further examples of partnering to accomplish important work.
“The pathway to success is going to be collaborative,” notes Valcarcel. “It’s going to involve a lot of organizations and people, similar to the path we’ve currently been on, but it will likely be expanding as we look to more habitats and locations for our reintroduction sites.”
The road to recovery for the northwestern pond turtle and northern leopard frog is a long one, but it’s a journey worth taking. By addressing threats, restoring habitats, and collaboratively boosting populations, WDFW and partners are building a future where these species can once again thrive.
Thanks to landmark biodiversity funding from the Washington Legislature, WDFW has been able to support a variety of actions to benefit both of these imperiled species. From CT scans and shell disease treatments for northwestern pond turtles; to reintroductions, site assessment, and genetic studies for northern leopard frogs, alongside bullfrog management in multiple locations to benefit both species, recovery efforts are yielding hard-earned results.
“It’s a balancing act,” Valcarcel said. “But with the right strategies, partnerships, and continued funding, we’re making progress. These species are part of what makes Washington unique, and it’s our responsibility to ensure they’re here for generations to come.”
