CONCORD, N.H. -- Winter surveys by biologists show that the deadly bat disease called White Nose Syndrome (WNS) is having a dramatic impact on New Hampshire's bat populations. Currently, five of the eight species of New Hampshire bats are affected by WNS, including the common little brown bat. One species, the northern long-eared bat, has now disappeared from hibernacula (bat wintering places) all over the Northeast.
Monitoring bat populations for the devastating fungus has become a necessary regimen in recent years, but biologists dedicated to managing bats and other nongame species in New Hampshire were particularly discouraged by their findings during a February survey of a Grafton County mine that is the second largest hibernaculum in the state. New Hampshire Fish and Game Department Nongame and Endangered Wildlife Biologist Emily Brunkhurst joined biologist Dr. Jacques Veilleux of Franklin Pierce University and Dr. Scott Reynolds of St. Paul's School for the midwinter survey of bat hibernacula in New Hampshire.
As Veilleux cut a hole in the ice covering the front of the mine, he encountered the first sign that all was not well within - a dead little brown bat encased in the ice. Climbing through the small hole, wearing protective gear to prevent the spread of WNS, the biologists looked down upon a gruesome scene: dozens of dead bats littered the floor or were frozen into the ice. Some 48 dead bats were found near the cave entrance, and more further in. The biologists proceeded with their grim duty - to count every bat in the mine, living and dead; recording the species and any signs of the WNS fungus (Geomyces destructains). In all, the biologists found 96 dead and 185 live bats in this mine, with 76 of the live bats showing evidence of WNS. This total of 281 bats was down by 83% from 2009.
"These are the worst indicators I have ever seen," Veilleux said sadly. "It was devastating to see this vibrant colony so decimated, and heart-rending to see a couple of the bats clinging to the walls, but obviously very, very sick."
The second survey of the day was conducted in a mine that does not get sealed in by ice. There, just one dead bat was found. "We could only assume that the sick bats had flown out of the mine and were either under the snow or had been eaten by predators," said Brunkhurst. As with the first site, the numbers of bats remaining in the mine were very low, down at least 50% from last year.
Over several weeks, the team surveyed six other New Hampshire bat hibernacula. Overall, numbers were way down, but a few encouraging signs emerged. In one small mine, which is heavily flooded (researchers wear wetsuits to conduct the survey), the bat population had increased from 48 bats in 2009 to 60 bats this year, with very little sign of WNS. Two very small hibernacula were discovered in old World War II bunkers, and no signs of WNS were apparent in the 83 bats found there. Statewide, however, bat population numbers were down significantly, for an overall population decline of 66% since last year.
In addition to surveying numbers of living and dead bats, the biologists looked for tiny silver bands on the bats' wings, markers placed during a survey of bats near New Hampshire hibernacula last fall. Individual identification numbers on each banded bat reveal whether the bat was captured at this hibernaculum or another, as bats don't always use the same wintering place from year to year. One theory as to why New Hampshire hibernacula actually saw increases in bat populations in 2009 was that bats stayed in the state instead of flying to Vermont to hibernate last year. WNS has hit hard in Vermont, which has the biggest hibernacula in New England, Aeolus Cave. Bats from all over New England, including ours in decades past, migrate there to hibernate for the winter. Before WNS, Aeolus cave had an estimated population of 200,000-300,000 bats. Now, bat numbers there have plummeted by as much as 90% -- a loss of tens of thousands of bats in a single hibernaculum.
As the winter progressed in New Hampshire, March brought a strange new phenomenon. Though it was much too early for bats to be leaving their hibernacula, many bats were seen flying in the Mt. Washington area, over the trail and base road, in the parking lots and at all altitudes. Several dead bats were collected by volunteers and U.S. Forest Service biologists for testing for WNS. "We aren't aware of a cave or mine hibernaculum in that area," says Brunkhurst, "but we are looking for one now, and it may have more bats than any known hibernaculum." Some of the live bats observed were big brown bats, which are known to hibernate in buildings, including the cog railway buildings, as well as caves and mines. (WNS has not been detected in bats living in buildings.) However, all the dead ones collected were little brown bats, which hibernate in caves and mines and are very susceptible to WNS, and the closest known hibernaculum is over 13 miles away.
Nationally, the rapid advance of the deadly bat disease is gaining attention. States that do not yet have WNS yet are busily planning their response and working with biologists and cave owners on this critical issue. National Geographic magazine dispatched a photographer to join the New Hampshire biologists on one of their recent winter surveys for a future story showing what state biologists, university researchers and the US Fish & Wildlife Service are doing to combat this destructive disease.
WNS first appeared in New York in 2006 and now has been documented in 11 states; it has expanded as far south as Tennessee and as far north as Ontario, Canada. Some of the spread can be attributed to migrating bats, but it is also feared that humans are transporting the fungus on their caving clothing and gear. Because of this, the US Fish & Wildlife Service requests all cavers to disinfect their gear between cave visits. In addition, do not bring any gear used in an infected state into a cave in an uninfected state, as disinfection procedures are not 100% effective, and respect all cave closures.
Why is the spread of WNS so important? Bats are the biggest predator of night-flying insects. Also, recovery from the onslaught of the disease will be difficult, because bats are slow breeders. They typically live a long life (over 20 years) and produce one, or rarely two, pups each year. As with most young of the year wildlife, not all pups survive, so rebuilding bat populations after such a rapid decline could take decades. "We don't know whether some of these bats will permanently disappear from the landscape, or exactly how the loss will change the ecology of our state," said Brunkhurst. "We may have more forest or agricultural pest issues, but it's just too early to tell."
Hundreds of scientists across the country are working to solve the mysteries of WNS. We know that the fungus is persistent - it remains in a cave and can infect bats that return there. Two types of treatments designed to control the fungus on the bats have been tested, but the results are not yet in. What is known is that it is extremely difficult to treat bats for fungus without also killing other native fungi in the cave ecosystem. Work is being done to see if surviving bats have slightly different genes than bats that have not yet been affected by WNS. Additionally, research is just beginning to look at why this very same fungus occurs on European bats, but does not harm them.
How can you help? If you have bats in your barn or house or other buildings, please try to leave them there, say biologists. Bats breed much more successfully in large colonies where the combined heat helps the young bats grow. If you have problems with guano, put a ceiling of plastic between the bats and your equipment, but DO NOT seal the bats in. Also, stay out of caves and mines, year round. The fungus can be picked up on clothing and gear, and transported to other sites. If you travel to a state which has not yet detected WNS, do not take any clothing or gear that has been in a cave or mine in the affected states (the entire Northeast and as far south as Tennessee). For more information, visit the N.H. Fish and Game website at www.wildnh.com/Wildlife/Nongame/bats.html.