NEBRASKAland Magazine is dedicated to outstanding photography and informative writing with an engaging mix of articles and photos highlighting Nebraska’s outdoor activities, parklands, wildlife, history and people.
Issue link: http://mag.outdoornebraska.gov/i/708333
64 NEBRASKAland • AUGUST-SEPTEMBER 2016 shown there are indeed peaks in activity in the late summer and fall when bats are migrating. This fall, a high-intensity survey will put more recorders in a smaller area, which could allow researchers to determine the speed and direction of the migration. Early data showed that microphones placed farther off the ground may better detect the movements of high-flying migrating bats. Some microphones recorded up to 1,400 calls in a single night, which could represent a few bats making many passes or many bats passing by. In 2015, a total of 580,000 bat calls were recorded from April to November. Among the findings, the acoustic recorders may lend credence to the study that places the value of bats to agriculture in the billions. Some question whether those findings, based on a small sample area near prime bat habitat, could be extrapolated across the entire agricultural landscape. The UNL recorders placed in agricultural areas, however, are recording a greater number of bat calls than anticipated. Another study, funded by the Nebraska Department of Roads, deployed 52 detectors across the state in 2015 to look for the northern long-eared bat. The work, which sampled 377 locations for six nights each, confirmed the range that previous sampling with mist nets had defined: eastern Nebraska, along the lower Platte River and along the Niobrara River west into the Pine Ridge. In 2016, the same 52 detectors are being deployed for a week in five different one-square-mile areas within the range to better understand how the species uses different habitats, including forest and water. The results will help the Department avoid bats during construction projects. A third acoustic study, funded by the Commission, will look at the distribution and habitat selection of all bats in Nebraska, deploying 20 stationary and three mobile detectors in 38 different locations. This data will be used for the new North American Bat Monitoring Plan, a nationwide effort t o collect data using acoustics, summer maternity colony and winter hibernacula surveys to identify population trends in all species on local, regional and range-wide levels. Nebraska is one of the first states to implement the program. UNL students will also be probing cracks and crevices with specialized cameras to search for maternal roosts. The acoustic detectors can do something researchers armed with mist nets cannot: be in the field night after night throughout the entire year, and be in many places at once. But the microphones are only able to record bats that fly within 25 to 50 meters, so while they can sample a larger area than mist nets, it is still relatively small. While the technology has been in use for more than 20 years, recent advancements, especially in software, improved its accuracy. Still, the technology is far from perfect when it comes to identifying species. The calls of some species are difficult to discriminate from others, and even the species that are believed to be easy to identify have varied calls. A study by Lemen, Freeman, White and a UNO student found that the four software programs used by bat researchers agree on the identification only 40 percent of the time. Some researchers, and even the creators of the software, worry this will lead those using the technology to draw the wrong conclusions. Because they are not foolproof, many believe acoustic data should always be backed up with netting, especially to confirm the presence of a species not normally found in an area. But researchers admit mist netting surveys are also biased, as they sample a minute area and some species are harder to catch than others. That said, Lemen, Freeman and White are using acoustic recorders themselves, sometimes simply to find the best places to set out their nets. In 2015, they used them to test a hypothesis that may be leading them to a new finding on northern long-eared bats. This forest species is known to primarily hibernate in mines and caves, which begged the question as to why they are found along the Missouri, Niobrara, and Republican rivers and in the Pine Ridge, but not the Platte River. None of these areas have the typical hibernacula, but all have plenty of woodland habitat, and all but the Platte have rocky cliff faces. Hypothesizing the bats were using cracks and crevices in these cliffs and rock faces, the researchers deployed their acoustic detectors in numerous areas across the state and found two rocky areas being used by northern long-eared bats, one near Ponca and another along the Little Blue River in Thayer County. This fall and winter, they will use Hundreds of big brown bats roost in gaps between concrete sections of an abandoned building at Camp Ashland, a Nebraska National Guard facility near Ashland.