Acoustic amphibian monitoring, 2018: Mississippi National River and Recreation Area

Casper, Gary; Nadeau, Stefanie; Kirschbaum, Al

The National Park Service Great Lakes Inventory and Monitoring Network (GLKN) established 10 permanent acoustic amphibian monitoring sites at Mississippi National River and Recreation Area (MISS) in 2015. Some sites were also monitored in 2014. Digital acoustic samples of 5-minute duration are collected by placing automated recorders with omnidirectional stereo microphones at each site. Temperature loggers co-located with the recorders collect air temperature during the sample period. Eight species of frogs and toads were found at MISS in 2018, with five species occurring at nearly every site: Eastern American Toad, Cope’s Gray Treefrog, Gray Treefrog, Green Frog, and Northern Leopard Frog. Blanchard’s Cricket Frog (State Endangered) continues to be found at only a single site. Wood Frog was detected at two new sites in 2018, and Boreal Chorus Frog was found at fewer sites in 2018 than in the prior two years. American Bullfrog and Spring Peeper remain undetected on any monitored sites, but a valid American Bullfrog record from Pig’s Eye was posted on HerpMapper.org and this species may spread. We expanded analyses and reporting in 2018 to address calling phenology, and to provide additional metrics for tracking changes in abundance across years. Abundance is tracked by assessing how the maximum call intensity changes on sites across years, and by how many samples with automated detections are reported across years. We also added analysis of false presence error rates for automated detection algorithms, which were <2% for most species in 2018 (slightly higher for Eastern American Toad (2.90%) and Green Frog (3.98%). No commission errors enter into site occupancy statistics as they are rejected by the proofing process. 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 limited to early battery failures apparently attributable to aging equipment. All equipment was replaced in 2019 with new more efficient units. Appendices present summaries of four years of cumulative results.

Acoustic amphibian monitoring, 2018: Mississippi National River and Recreation Area

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