Date of this Version
Natural Resource Report NPS/NGPN/NRR 2018/1588 / NPS 920/142392, February 2018: 15, 157 pages
Also available at: https://science.nature.nps.gov/IM/units/ngpn/index.cfm
Please cite this publication as:
Licht, D. S. 2018. Acoustic Surveys of Bats at Northern Great Plains Parks and Preliminary Results from 2014-16. Natural Resource Report NPS/NGPN/NRR—2018/1588. National Park Service, Fort Collins, Colorado.
From 2014-16, the Northern Great Plains Inventory & Monitoring Network (Network)—in collaboration with the Midwest Regional Biologist—used acoustic methods to monitor bat populations at 12 Network parks. Six parks were monitored using the nascent North American Bat Monitoring Program (NABat) framework. Six other parks did not meet a priori criteria for inclusion in NABat so they were monitored using similar methods, but a non-systematic sampling frame.
Fifty-five NABat stations were established along with 62 non-NABat stations. Stations were typically monitored for 4-7 nights each year using equipment that records the echolocation calls of bats. Fourteen mobile survey routes (24-47 km, 14-28 miles) were also established, one for each NABat sampling cell. Two night-time surveys were conducted per route each year. The recordings were analyzed using specialized software that uses probabilistic statistics to classify the species that made the call. A total of 1,573 nights and 847,321 bat recordings were analyzed from the stationary points. A total of 70 driving surveys were conducted, collecting another 2,439 recordings of bats.
A review of the software output indicates that 14 bat species are present in the Network (Figure ES-1). There were substantial differences in bat communities between parks, an apparent consequence of the variety of habitats in the Network and the vast size of the region as both “eastern” species and “western” species were detected. The northern long-eared myotis is the only federally-listed species in the Network. It was confirmed in several parks, but was not common in any parks.
A primary purpose of the project is to monitor changes in bat abundance over time. Across the 29 NABat stationary points with usable data from all three years the average number of nightly bat detections at a station was 746 in 2014, 617 in 2015, and 865 in 2016 (unweighted by the length of the deployments; see Figure ES-2 for average number of nightly bat detections at each NABat station). At the eight mobile routes surveyed in all years the average number of detections per route was 41 in 2014, 34 in 2015, and 33 in 2016. In neither case were the Network-wide between-year differences statistically significant. However, there were some substantial differences between years at some stations and some parks. For example, at the Missouri NRR there was a large drop in the rate of detections from 2014 to 2015, but detections rebounded in 2016, highlighting the importance of monitoring for several years before assessing long-term trends in bat populations.
Park managers can take actions to conserve bats. The highest rates of detections were typically from stations near water. In forested areas decadent trees and other woody material should be protected, specifically, trees with exfoliating bark and cavities as these provide roosting habitat for many bat species. Fort Laramie successfully established a bat house as mitigation for keeping bats out of historic structures. Education programs are important in garnering support for bat conservation.
In late 2015 the Network established an agreement with the University of Wyoming to monitor bats at the six NABat parks from 2016-20. The Midwest Regional Biologist will assist the monitoring and will attempt to monitor the non-NABat parks as well. Hopefully, bat monitoring will become a permanent component of the Network monitoring program.
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