February 12, 2013
In North Carolina, endangered Virginia big-eared bats are known from only two caves at Grandfather Mountain, where they hibernate.
What has puzzled biologists for years is where these bats go in the summer to give birth. This spring a massive effort aims to answer that question.
About 12,000 Virginia big-eared bats are known to exist in four states and 400 of those hibernate in the Grandfather Mountain caves. This species typically hibernates in one place, and with warmer weather the two sexes each migrate to different locations for the summer, with the females departing to give birth and rear their young in a maternity colony.
This migration is limited, with bats usually moving less than 20 miles from their hibernation site. It’s known that some males summer on a viaduct at Grandfather Mountain, and the females are expected to be somewhere in the rugged, remote, and sparsely populated areas surrounding Grandfather Mountain, though no one knows where.
“Finding those bats will not only solve a mystery, but will also get us a few steps closer to removing these bats from the endangered species list,” said Joy O’Keefe, an assistant professor at Indiana State University who is heading the search.
Knowing where the endangered bats maintain their maternity colony would allow biologists to help conserve the sites.
“This will give people and organizations that are planning construction projects, like the North Carolina Department of Transportation, a clearer idea of special areas to keep in mind during project planning,” said Sue Cameron, a biologist with the U.S. Fish & Wildlife Service. “At the same time, it’ll tell wildlife biologists where to focus conservation efforts.”
The proposed widening of North Carolina Highway 105 spurred the project, and led the N.C. Department of Transportation to fund the three-year effort. Knowing where the maternity colonies are will enable the NCDOT to avoid impacting the bats as they widen the highway and develop new transportation projects in the area. The effort will also provide additional information on routes the bats take between winter and summer sites, and help identify areas where the they forage for food.
In early spring, as the bats begin to emerge from hibernation, biologists will attach tiny transmitters to their backs. The challenge for the biologists is to keep track of the radio signal coming from the bats as they cross the area’s rugged terrain. The signals can be blocked by rock, easily being lost should a bat duck into an unknown cave.
In recounting a previous effort to find the bats, O’Keefe remarked, “They never found a maternity roost. Bats seemed to just disappear on the landscape.”
Tracking the signal this time will be a three-pronged effort. First, four temporary towers, each about 30 feet tall, will be strategically placed on high mountain peaks. The towers will be equipped with data loggers that will record information every time it picks up a transmission. Secondly, there will be teams of biologists on the ground with receivers, driving the area to pick up signals. The effort’s third prong should really boost the chances of success – an airplane will fly the area picking up the transmitter signals from above, where they won’t be hampered by signal blockages from rock outcrops or ridgelines. Signals picked up from the air will also help guide the ground crews.
The plane is provided by Copperhead Environmental Consulting, a Kentucky-based company starting to establish a reputation for tracking bats from the air. Last year they tracked a pair of endangered Indiana bats from Tennessee; one into Alabama, and one into Georgia, marking the first known occurrence of that species in Georgia in over 50 years.
This activity will be packed into a two-month period, after which the transmitters’ batteries will go dead and the airwaves will go silent. Eventually the bats will shed the transmitters. Biologists plan to duplicate the effort in the spring of 2014, then use the collected data to deduce the locations of the maternity colonies. Another Virginia big-eared bat study is underway in Kentucky, and it’s hoped information from both studies can be combined to provide a broader understanding of the ecology of the species.
The effort brings together biologists from Indiana State University, N.C. Department of Transportation, U.S. Fish & Wildlife Service, N.C. State Parks, Grandfather Mountain, N.C. Wildlife Resources Commission, and Copperhead Consulting.