Acoustic amphibian monitoring, 2018: Indiana Dunes National Park

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 Indiana Dunes National Park (INDU) 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 detected in 2018, with five species occurring at nearly every site: Eastern American Toad, Gray Treefrog, Green Frog, Spring Peeper, and Boreal Chorus Frog. Three species—American Bullfrog, Northern Leopard Frog, and Wood Frog—were detected on less than half of the monitored sites. No detections were confirmed for two species thought to be extirpated: Blanchard’s Cricket Frog and Fowler’s Toad. Data collection issues in 2018 were generally good and cumulative multi-year results are provided. However, most recorders stopped logging before the desired end date, presumably due to battery drains, which reduced the number of detections for late-calling species. Replacement of the original aging ARS units in 2019 with new, more efficient units should resolve battery life issues moving forward. Monitoring at Site INDU06 was discontinued in 2016 due to worries over vandalism. We recommend re-starting data collection at Site INDU06 to meet the program goal of 10 monitored sites. We can assist with repositioning the ARS within the same wetland, or with finding a new monitoring site, based on program site selection criteria. We expanded analyses and reporting in 2018 to address calling phenology and to provide additional metrics 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 false presence error rates for automated detection algorithms, which were less than 3.5% in 2018 for all but one species. 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. Appendices present summaries of five years of cumulative results.

Acoustic amphibian monitoring, 2018: Indiana Dunes National Park

Series

See also

Collections