Acoustic amphibian monitoring data summary report for Apostle Islands National Lakeshore: 2018

Casper, Gary; Nadeau, Stefanie; Kirschbaum, Al

Amphibians are a Vital Sign indicator for monitoring long-term ecosystem health in nine national park units that comprise the Great Lakes Network. We present here the results for 2018 amphibian monitoring at one of those parks––Apostle Islands National Lakeshore. Appendices contain tabular summaries of four years of cumulative results. The National Park Service Great Lakes Inventory and Monitoring Network (GLKN) established 10 permanent acoustic amphibian monitoring sites at Apostle Islands National Lakeshore (APIS) in 2014. Acoustic samples are collected by placing automated recorders with omnidirectional stereo microphones at each of the 10 sample sites. Temperature loggers co-located with the recorders collect air temperature during the sample period. Six species of frogs and toads were detected in 2018, with Green Frog and Spring Peeper occurring at each of the ten sites. Mink Frog was found at only two sites in 2018. Northern Leopard Frog, American Bullfrog, and Boreal Chorus Frog are found near or within the park but have not yet been detected at any network monitored sites; none were detected in 2018. Eastern American Toad, Gray Treefrog, and Wood Frog were not detected at some sites where they were detected in prior years. We expanded analyses and reporting in 2018 to address calling phenology, and to provide a second metric for tracking changes in abundance (in addition to occupancy) across years. Abundance is tracked by assessing how the maximum call intensity changes on sites across years, and by how many automated detections are reported from sites across years. We also added analysis of error rates for automated detection algorithms, most of which were less than 5%. The dual survey approach with large sample sizes continues to return reliable results, providing a near-perfect record of site occupancy for most species. False absences are accounted for in periodic occupancy modeling. False positives for site occupancy are eliminated by dual observer proofing. Data collection issues in 2018 were minimal.

Acoustic amphibian monitoring data summary report for Apostle Islands National Lakeshore: 2018

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