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After six years and thousands of euthanized bullfrogs, a campaign to control the invasive species in the Upper Deschutes Basin is starting to show results. The number of bullfrogs visible in pools of water around Sunriver is on a downward trend, says Jodi Wilmoth, owner of 3 Rivers Environmental , a consultancy that specializes in habitat restoration and the control of invasive species. “There are definitely fewer bullfrogs in the areas that we have had a multiyear effort in,” said Wilmoth, who spends her summers leading a small team to remove bullfrogs from riverbanks and ponds near Sunriver.
“Our real goal is to be able to see an increase in Oregon spotted frog egg masses in areas that we have removed bullfrogs.” The invader: the bullfrog is an invasive species in Central Oregon. The Oregon spotted frog, a native species in the Upper Deschutes, is listed as threatened under the Endangered Species Act.
The frog has lost habitat across its range in the Pacific Northwest and is particularly vulnerable when stream flows change due to dams and diversions. The invasive bullfrogs — introduced in the early 1900s as a food source — also pose a threat as they prey on the smaller spotted frog. Bullfrogs also compete for available food sources and take over spotted frog habitat.
Wilmoth and her team are trying to even the score by removing bullfrogs and their egg masses. Over the past six years, her team has euthanized 7,131 bullfrogs in the Upper Deschutes Basin. The main source of funding for bullfrog removal is the Upper Deschutes Conservation Fund , which comes primarily from parties to the Deschutes Basin Habitat Conservation Plan , including the eight irrigation districts operating in Central Oregon.
Read More: One woman's nightly war on bullfrogs Funding levels for bullfrog eradication have increased over the six-year project, allowing Wilmoth to hire more assistants and capture more bullfrogs. This year, Wilmoth and her team rounded up and disposed of 2,125 bullfrogs, more than in the first three years combined. The number of bullfrog egg masses collected each summer is also increasing.
Last summer 87 egg masses — which contain hundreds or sometimes thousands of eggs — were collected and destroyed. The previous high was 50 egg masses removed in 2019. Some areas where the bullfrog removals occurred have experienced gains in spotted frog egg masses, Wilmoth says.
There is a caveat because the number of egg masses also depends on water levels in the Little Deschutes River, where she primarily operates. Wilmoth doesn’t conduct searches for bullfrogs in the main Deschutes because the frogs are rarely, if ever, found in that river. Bullfrogs struggle to survive in the big Deschutes because of water management practices for agriculture, she said.
As for the increase in bullfrog captures year-over-year, Wilmoth attributes that to funding increases as the project moves along. More funding each year allows her to hire more staff, and with more staff they can cover more ground and capture more frogs. Wilmoth stresses that complete eradication of bullfrogs in the Upper Deschutes is unlikely and the best that biologists can do is control their numbers.
Sites with known Oregon spotted frog populations are given priority to hunt for bullfrogs, these include the Little Deschutes River from Crescent Lake to the confluence of the big Deschutes River. Jodie Delavan, a spokesperson for U.S.
Fish and Wildlife Service, says the Upper Deschutes Watershed Council has been instrumental in allocating funds to work with landowners interested in bullfrog removal. “These removal efforts are guided by technical expertise within federal and state wildlife agencies and private consultants,” said Delavan. “Current efforts are underway to monitor the rate of bullfrog expansion in the Deschutes and Little Deschutes river systems and to develop effective management techniques for control.
” Delevan says the Fish and Wildlife Service does not yet have funding allocated in 2025 for bullfrog control in the Deschutes Basin but she anticipates bullfrog removal work will continue “as funding and capacity allow.”.
