Acoustic amphibian monitoring, 2019 data summary: Sleeping Bear Dunes National Lakeshore

Abstract

Amphibians are a Vital Sign indicator for monitoring long-term ecosystem health in seven national park units that comprise the Great Lakes Network. We present here the results for 2019 amphibian monitoring at Sleeping Bear Dunes National Lakeshore (SLBE). Appendices contain tabular summaries for six years of cumulative results. The National Park Service Great Lakes Inventory and Monitoring Network established 10 permanent acoustic amphibian monitoring sites at SLBE in 2013. Acoustic samples are collected by placing automated recorders with omnidirectional stereo microphones at each of the 10 sampling sites. Temperature loggers co-located with the recorders also collect air temperature during the sampling period. We expanded analyses and reporting in 2018 to address calling phenology and to provide a second metric for tracking changes in abundance across years. Occupancy analyses track whether or not a site was occupied by a species. 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. Using two independent survey methods, manual and automated, with large sample sizes continues to return reliable results, providing a confident record of site occupancy for most species. The monitoring program detected five of the six species of frog and toad known to occur at SLBE in 2019, with Eastern American Toad, Gray Treefrog, Green Frog and Spring Peeper occurring at almost every site sampled. Wood Frog was found at one new site, and Northern Leopard Frog was not confirmed in 2019 but was detected at five sites in 2018. There were no significant data collection issues in 2019 except for late deployment of SLBE11, which limited data analyses for this site. Remaining sites successfully collected data as programmed. Cumulative data collection result summaries since inception are provided in appendices. Since temperature logs show that the threshold of ≥40°F was often exceeded by 1 April in 2019, making 15 March a start date for data collection may be considered if park personnel feel snow and ice cover would be reduced enough by that date as well.