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Bat Research Provides Valuable Information for Great Swamp Refuge and Beyond
by Jennifer Bohrman
Photo Credit: Andrew King, USFWS
If you're out at Great Swamp National Wildlife Refuge in New Jersey just before sunset, you may catch a glimpse of a returning summer resident, sweeping through the twilight like a flickering, acrobatic shadow. If you're especially observant, you may notice that these winged silhouettes look slightly bigger than they did a few years ago.
From 2006 through 2010, research showed that the refuge offered ideal habitat for the endangered Indiana bat (Myotis sodalist), and at the time, supported several maternity colonies of Indiana bats. The little brown (Myotis lucifugus), northern (Myotis septentrionalis), tricolored (Perimyotis subflavus), big brown (Eptesicus fuscus), and eastern red bat (Lasiurus borealis) are some other common bat species known to spend summers at Great Swamp.
But during this time, white-nose syndrome (WNS) hit northern New Jersey. The rapidly spreading fungal disease has devastated populations of hibernating bats across the U.S. since its discovery in 2006.
In the summer of 2012, employees at Great Swamp National Wildlife Refuge began piecing together the impacts of WNS on refuge bats. Annual capture rates of small bats – Indiana, little brown, northern and tricolored bats – plummeted, while capture rates of larger species, including big brown and eastern red bats, began to gradually climb. Unlike before the local outbreak of WNS, considerably more large-bodied bats than small-bodied bats were captured.
Photo Credit: Jenny Bohrman
At the same time, acoustic surveys detected significantly more large-bodied bat echolocation calls across the refuge. Wing damage and skin swab samples provided further evidence that refuge bats were exposed to the fungus that causes WNS. These collective results confirmed that WNS has taken a severe toll on the Indiana bat and other small, cave-hibernating species on the refuge. Despite these findings, biologists currently do not know why some species appear to be more susceptible to WNS than others.
Historically, refuge management focused primarily on the habitat requirements of the endangered Indiana bat. With several bat species now threatened by WNS, management consideration has evolved to include other susceptible species, including little brown and northern bats.
Using radio telemetry, little brown and northern bats are occasionally tracked to manmade structures. Their tendencies to use artificial roosts suggest that bat boxes may be a valuable conservation tool. This past spring, 20 bat boxes, made available through the William Paterson University, were installed across the refuge. A graduate student will assess the occupancy of these bat boxes and continue annual acoustic surveys. The research is expected to provide information on the preferences of bats using artificial roosts, such as the design of the artificial boxes they might use.
Great Swamp's uniquely rich, long-term database on bat foraging and roosting ecology has been valuable in documenting reproductive colonies and identifying local ecological requirements and preferred habitats for a federally endangered species. In light of recent dramatic declines in Indiana bats and other bat species, continuing annual summer research is critical for informing future management practices and informing state and federal listing decisions.
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