While few people think of a cold, dark, and wet cave as animal “habitat,” that’s exactly what it is for many of Pennsylvania’s bats — at least for about half of the year.
Six of Pennsylvania’s nine bat species enter natural or man-made caves each winter when their food supply of insects disappears. It is here these bats seek out a location with a constant temperature below 50 degrees, hang upside down by their thumbs, and reduce their metabolic rate. Heart rate and breathing slows, body temperature drops, and signs of life become hard to discern. They will not stir again until the weather warms come springtime – when aerial insects and the bats themselves, once again take flight.
Pennsylvania cave-bat species include the little brown, big brown, northern long-eared, small-footed, tri-colored and Indiana bat. The Indiana bat is a federal and state-listed endangered species and considered a “priority species” in the Game Commission’s wildlife action plan. Tree bats include the red, hoary, and silver-haired bat. In the winter months these species migrate south, where warmer weather and abundant insects remain available.
Abandoned coal mines harbor life
The 1762 discovery of anthracite coal near the town of Pittston, Luzerne County, initiated a series of events that would drastically change the landscape of northeastern Pennsylvania. The population of the anthracite “coal region” grew rapidly after the Civil War, as immigrants from Russia, Poland, Italy, Wales, Ireland, Lithuania, and other countries poured into the area to supply an ethnically diverse labor force. The anthracite mining industry loomed over the region until its dramatic decline in 1950s, leaving behind miles of abandoned mine shafts and other underground spaces that made ideal winter hibernacula for bats. Slope-type mine shafts provide the vast majority of winter habitat for cave-bats in northeastern Pennsylvania.
Pennsylvania cave-bats have been sharing their winter quarters for nearly a decade with an unwanted guest in the form of a cold-loving fungus that has been decimating their populations.
White-Nose Syndrome was first documented in New York in the winter of 2006-07 and is believed to have surfaced in Pennsylvania in 2008. Evidence suggests the fungus originated in Europe, where bats are immune to the disease, and probably spread to North America through human activity such as spelunking.
The disease, which affects all of Pennsylvania’s cave-bat species, refers to a white fungus that accumulates on the muzzles and wing membranes of affected bats. The fungus, called Pseudogymnoascus destructans, causes bats to arouse from hibernation too frequently, causing a severe depletion of fat reserves needed to survive the winter. Unusual behavior exhibited by affected bats include bats flying outside during the day in temperatures below freezing and clustering near the entrances to hibernacula. Dead or dying bats are often found on the ground near a cave or mine entrance.
Pennsylvania Game Commission diversity biologists conduct a variety of surveys throughout the year to monitor bat population trends and identify habitats in need of protection.
Caves and mines are visited each winter to count bats and document species. Winter-hibernacula surveys are conducted under a strict operational protocol that minimizes bat disturbance and prevents cross-contamination of other hibernation sites.
Bats are trapped and tagged using mist nets during spring emergence and fall swarming to identify emergence times and migration habits.
Game Commission staff and the public participate in the annual Appalachian Bat Count to monitor summer maternal colonies in bat boxes, barns, and other dwellings.
More recently, agency biologists also conduct acoustic transect surveys to record bat calls along established 20-mile survey routes.
Bat numbers plummet
Most hibernacula sites in Pennsylvania have been affected by the fungus that causes WNS and the percent of bat mortality likely differs by site and by species.
Little brown bats have been the species hit hardest, with nearly 100-percent mortality documented since the onset of WNS in the Commonwealth. The endangered Indiana bat continues to suffer devastating losses and other state cave-bat species experienced serious declines as well.
The PGC, other state wildlife agencies, and a coalition of cooperating research institutions identified the treatment and control of WNS as one of their highest priorities.
When many of the coal mines were closing, pillars of coal-supporting mine ceilings were systematically pulled or “robbed” to extract as much coal as possible as miners made their way back to the shaft opening.
This practice resulted in highly unstable and unsafe underground spaces.
Many shaft openings were blasted shut for public safety, but others remained open, attracting both bats and humans. Efforts to protect natural cave and abandoned coal mine openings in northeastern Pennsylvania have been underway for decades but the importance of protecting hibernating bats has become more critical since the advent of WNS.
To date, nearly 30 cave and mine openings have been gated in the Game Commission’s Northeast Region to protect bats and the public.
An abandoned railroad tunnel close to Interstate 81 on state game lands in southern Luzerne County historically held four different species of bats, all in low numbers.
The large opening at the mouth of the tunnel was allowing cold air to escape, preventing the interior space from maintaining the optimal temperature range for hibernating bats.
The Game Commission developed a plan to improve habitat conditions in the tunnel, allow access for bats, and prevent disturbance by people. A gate was installed at the entrance to the tunnel and an earthen embankment was positioned in front of the entrance to help maintain an ideal temperature range within the mine. Compensatory funding provided to offset habitat losses due to development elsewhere was used to improve and protect this hibernaculum. The project was completed in the summer of 2017.
One of the oldest coal mines in the Game Commission’s Northeast Region is located on State Game Lands 57 atop Bartlett Mountain in Forkston Township, Wyoming County. An article from the Wyoming Democrat printed in August 1871, described the coal there as being of marginal quality, and the surrounding area as “offering lovely points of view of the wild valley below.”
Game Commission staff coordinated with personnel from the state Department of Environmental Protection’s Bureau of Abandoned Mine Reclamation to provide oversight and funding for the construction of a gate at this site. The project was completed in summer 2017 and improvements to nearby Coal Mine Road enhanced hunter access in this area.
Several years ago, Game Commission staff discovered approximately 12 historic mine openings in a remote portion of State Game Lands 36 in Bradford County. The coal industry peaked here in the 1880s, and by the 1890s, local industry transitioned to support the growing lumber boom. Agency wildlife biologists conducted winter hibernacula surveys in early 2016 and found bats actively using three of these mines. The three active mine openings were gated to protect these sites.
Where there is life…
Northeast Region Wildlife Management Supervisor Kevin Wenner is hopeful that cave-bat populations in northeastern Pennsylvania can recover from the devastating effects of WNS.
“Despite the losses cave-bat populations have experienced as a result of White Nose Syndrome, small numbers of these species are persisting almost 10 years after the introduction of this devastating disease,” Wenner said. “Hope exists that remaining bat populations will build a resistance or develop ways to combat this deadly fungus.”
In the meantime, the Game Commission’s Northeast Region will continue efforts to improve, protect and preserve the critical habitat these bats species rely on so their populations can exist for years to come.