LITTLE ORLEANS - Clouds drift in front of a nearly full moon as a bat flutters to the mouth of an abandoned railroad tunnel in Western Maryland. There, caught in a web of fishing line, it drops into a biologist's trap.
A quick and gentle exam by flashlight identifies it as a big brown bat, a female. Gloved hands jot down her vital statistics and release her - one more data point in scientists' growing understanding of what is believed to be Maryland's largest winter hideaway for bats.
The 4,350-foot Indigo Tunnel southwest of Hancock hosts an estimated 1,400 bats during their winter hibernation, some of them rare and endangered species. But the bats' fondness for the place could derail plans to extend a popular bike trail through the cavernous tunnel - a route that supporters hope will help lure thousands more tourists to this hard-pressed region.
In 2005, the administration of Gov. Robert L. Ehrlich Jr. set aside $4.6 million in state and federal funds to extend the Western Maryland Rail Trail, a 22-mile paved biking path, for 4.7 miles through Indigo Tunnel to the hamlet of Little Orleans in Allegany County.
Eventually, boosters want to extend it farther, traversing the Stickpile and Kessler tunnels to Paw Paw, W.Va.
Public officials on both sides of the Potomac River think the rail-trail extension could bring more bikers, hikers and in-line skaters, and their money. "In Hancock in the summer, you see all kinds of people in town on bikes. They stop there and eat and buy other things," said state Sen. George C. Edwards, a Republican who represents Western Maryland.
There are ways to extend the trail while bypassing the tunnel, but it wouldn't be the same, say supporters who believe the trail could become one of the nation's top cycling destinations.
"Anytime you can include a 100-year-old historic tunnel in your trail, that kinda gives you bragging rights," said Penny Pittman, a restaurant owner and president of the Hancock Chamber of Commerce.
Human recreation and bats can sometimes coexist, says Jim Kennedy, a biologist with Texas-based Bat Conservation International: "But in this case, we really don't see a clear way that the bike trail is going to have any beneficial or benign effects on the bats."
He worries that human presence in the tunnel, and alterations for bike traffic, would make it unattractive to bats.
Harvey Bryant, manager for the project at the Maryland Department of Natural Resources, said his agency "will do whatever is necessary to protect the bat species, since they are endangered."
Final decisions on the tunnel's future are a year away, after completion of an environmental assessment by the University of Maryland's Appalachian Laboratory in Frostburg. The findings will go to DNR and ultimately to the National Park Service, which owns the property as part of the C&O; Canal National Historical Park.
The single-track Indigo Tunnel was built in 1904 and served until the Western Maryland Railway abandoned it in 1975. Shored up by wooden cribbing, the 20-foot rock walls are largely exposed. The roof is covered by wooden planking.
There were few bats there when it was abandoned, said Dana Limpert, a DNR ecologist. But it has since become the largest known bat hibernaculum in Maryland. It also appears to be the last major redoubt of the Eastern small-footed myotis.
This tiny bat is listed as endangered in Maryland, rare in West Virginia and threatened in Pennsylvania. Its two largest hibernacula, both in New York state, have been devastated since 2006 by "white nose syndrome." Over two winters, the spreading fungal infection has killed hundreds of thousands of bats in New York and New England.
"We are expecting to lose the Eastern small-footed myotis up in the Northeast," said Aimee Haskew, 29, a faculty research assistant at the Appalachian Lab. "It's possible ... this will be their last large hibernaculum range-wide. Given the conservation status of the species, under state law they warrant protection."
Strolling through the silent, dripping tunnel one night this week, she swept a flashlight beam across solitary bats sleeping on the rock walls. Some ceiling supports have rotted and collapsed, and piles of fallen rock litter the floor.
If the trail goes through, DNR officials said, they would replace the rotted wood; install dim, cool, LED lighting near the floor; and clear fallen rock. But they also would gate both portals so humans could be kept out at times, while still allowing free access to bats.
As a scientist, Haskew insists she is neither for nor against development of the tunnel. But after working with bats for more than four years, she is worried. "They're fascinating creatures, so misunderstood ... such underdogs," she said. "I just don't want to hurt the bats."
At least three species have been seen hibernating in Indigo Tunnel: little brown bats; big brown bats and Eastern pipistrelles. But trap surveys in spring and fall suggest there are more. They have snared long-eared bats (on the federal endangered species list), silver-haired bats, Eastern red bats, Northern myotis and a solitary Indiana bat, also federally endangered.
Nature's only flying mammals, bats play important roles in plant pollination, seed dissemination and pest control. One little brown bat can devour 1,000 mosquito-sized bugs an hour, Haskew said. Bats also eat agricultural pests, sparing farmers $1 billion a year in crop losses and insecticide costs.
At Indigo Tunnel, electronic devices record temperature, wind and humidity throughout the tunnel so scientists can map the conditions preferred by each species. An acoustic recorder monitors bat calls at the tunnel's mouth, and radio transmitters glued to a half-dozen silver-haired bats allow the team to track their movements.
On this cold November night, Haskew and lab employee Katie Parsh, 24, wait for bats to fall into their traps at the tunnel's east portal. Jamie Utz, 24, and Risa Wright, 22, work the west end.
In warmer weather they have caught more than 80 bats in a night. But it's cold now, and it's more than an hour before Haskew scoops the first big brown bat from her trap. "She's a girl, pretty young," she says, judging age by bone growth in the bat's translucent wings. The bat chatters angrily, trying valiantly to bite Haskew's gloved hand and wriggle free.
Weighed in a plastic sandwich bag, the bat tips the scale at a fat and healthy 21 grams - less than an ounce. The small-footed myotis typically weigh just 5 grams.
After curling an identifying band around the bat's forearm, Haskew sends it fluttering off into the moonlit woods.
At present, the Western Maryland Rail Trail follows the old railroad bed along the Potomac, roughly paralleling the C&O; Canal's dirt and gravel towpath trail.
For cyclists with thin-tired road and racing bikes, the paved trail offers a smooth ride. The towpath's mud, tree roots and narrow tracks are better suited for mountain bikes.
"It gets rough enough you have to walk," said Richard Cushwa, president of the Cumberland Valley Cycling Club.
An extension to Paw Paw, adorned by old tunnels and bridges, would be a scenic and speedy link in the long towpath ride from Georgetown to Cumberland, and from there along the Great Allegheny Passage trail to Pittsburgh.
Rail tunnels are not normally good bat hibernacula, according to Bat Conservation International. Smooth, straight and wide open at both ends, they offer fewer hiding places than natural caves and expose hibernating bats to cold, drying winter winds.
The fact that so many bats use Indigo anyway, Kennedy said, "shows there aren't any better roosts nearby. ... That makes the site a much higher priority for conservation because there aren't any options for the bats to go to."
Kennedy's report to the DNR did not oppose running the rail trail through the tunnel. Instead, it suggested a range of options.
Best for the bats, it said, would be to close the tunnel at one end, seasonally or permanently, stabilizing winter temperature and humidity. Bikers could bypass Indigo by transferring to the nearby unpaved towpath for about a mile and a half.
The tunnel could even be developed for bats and bat-watchers during the fall swarming season. Kennedy said Old Tunnel and Clarity Tunnel in Texas are both managed specifically for bats: "Old Tunnel attracts tens of thousands of people a year."
Edwards expressed hope for compromise. "They all need to sit down at the table and talk about it," he said.