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Connecting and expanding amphibian monitoring in Western Washington

Various non-profit, government, and academic entities study and monitor amphibian populations in the Pacific Northwest, however there are limited resources for data-sharing and coordination among these entities. Oxbow Farm & Conservation Center, in collaboration with Woodland Park Zoo, has been working to address these gaps. As a first step, Oxbow and Woodland Park Zoo staff distributed a questionnaire on monitoring activities and perceived needs to individuals representing non-profit, government, tribal, and academic institutions involved in amphibian monitoring. Together, the 23 respondents’ institutions monitor over 200 sites annually (from Canada to Oregon, but mostly in western WA) and engage 140+ community volunteers annually in these efforts. The most common observations regarding gaps in current monitoring efforts were these:

  • Improvements to monitoring capacity are needed in this region, including better funding and more capacify to hire and retain staff for this work, better coordination and data-sharing capacity among groups and agencies, and more standardized, shared protocols.
  • More and better data on population trends and distribution of species across the region are also needed, including long-term datasets for common as well as listed species.
  • Invasive species, including bullfrogs, are a major concern.

Better integration and data-sharing could help guide and inform monitoring institutions as well as providing important information for wildlife managers and conservation decision-makers. Oxbow and Woodland Park Zoo are in the process of organizing a working group to further consider these issues.

Accurate characterization of the status of amphibian populations in Washington is made difficult in part due to limited capacity to monitor rural habitats and a limited understanding of the distribution and quality of these habitats. From a wildlife conservation perspective, Agricultural Production District (APD) and Forest Production District (FPD) working lands in King County represent a large proportion of the lowland habitat in the county that is not heavily impacted by urban/suburban development. Better spatial information on the relative density of wetlands in these habitat types would help to contextualize the likely habitat value of these lands for different amphibian species. We analyzed National Wetland Inventory (NWI) spatial datasets for low elevation (<2000’ ASL) land within the Snoqualmie River watershed and showed that freshwater emergent wetland comprised 6.0% of land within the heavily farmed APD and only 0.26% of land in the Forest Production District (a 23-fold difference). Despite greater forest cover in the FPD, forested wetlands made up 7.4% of the APD land and only 1.7% of the FPD. This comparison shows that, due to the presence of extensive floodplain wetland features in the APD, this district represents an outsized proportion of potential breeding ponds for amphibian species that can persist in an agricultural landscape. Working with the farming community, opportunities may also be found to support populations of more sensitive species like northern red-legged frog through selective floodplain forest restoration.

Oxbow continues field efforts to monitor two pond complexes where floodplain restoration activities have been carried out. At Keller Mitigation Bank, where new wetlands and channels were excavated in 2020, few amphibians were observed in the first year of vegetation development (2021). In spring of 2022, ponds and channels were sites for oviposition by long-toed salamanders (Ambystoma macrodactylum), Pacific tree frogs (Pseudacris regilla), northwestern salamanders (Ambystoma gracile), and northern red-legged frogs (Rana aurora aurora), indicating successful establishment of viable amphibian breeding habitat. In Cherry Valley wildlife management area, where two ponds have been enhanced in 2020 by floodplain forest plantings, fluctuations in egg mass abundance were observed, with two ponds showing reduced abundance of northwestern salamanders from 2021 to 2022. Conversely, northern red-legged frogs were more widely observed in ponds in 2022. These changes are unlikely to be linked to vegetation development, given the limited structural changes at this point. Minnow trapping in 2021 also allowed discovery of populations of neotenic (permanently aquatic) northwestern salamanders at this site. Monitoring will continue to better understand the ways amphibian populations change as plantings mature.