A few days after a fire destroyed a historic covered bridge in Cornwall last month, Alyssa Bennett, a biologist with the Vermont Fish and Wildlife Department, drove out to the site at dusk to see if a colony of endangered little brown bats had survived. She wasn’t the only onlooker: a number of people had driven out to the bridge to view the damage and, through the glare of their headlights on the opposite shore, Bennett could see bats flying in and out of the charred structure.
It was a good sign. Bennett counted 10 bats that night which represented about 10 percent of the swamp road colony at that time. That same night at a sister colony further north Bennett found a slightly higher percentage of bats suggesting that the impact of the bridge fire may have been minimal. Being late summer, she said, most of the young males had probably dispersed and adult females had begun to make the journey back to their winter breeding habitats.
“If it had happened in mid-summer when pups couldn’t fly,” Bennett said, “it would’ve been devastating.”
It’s hard to overstate the significance of the swamp road colony. It’s one of only two summer sites in the state for which there is data stretching back to 2006 before the onset of white nose syndrome, a fungal disease that has ravaged bat populations throughout the northeast. Indeed prior to white nose, which was first discovered in caves near Albany, bat colonies in Vermont were so common and so vast, sometimes numbering in the thousands, that they weren’t closely monitored. Moreover the swamp road colony had been pretty stable. Bennett estimates that there were about 200 bats inhabiting the bridge in 2006, when they first collected data. Earlier this summer they counted 181. In late July, the last count before the fire, there were 95.
The fire was first reported around 2.30 p.m. on Saturday, Sept. 10. Cornwall Fire Chief Dennis Rheaume, who lives on the other side of Route 30 on West Street, could see smoke rising from swamp road as soon as he reached a high point. By the time he approached the bridge there were flames shooting out of the structure’s western entrance at least 50 feet in the air. Soon after, the roof collapsed. Leaves on nearby trees were incinerated and hot ashes scattered in the breeze. Rheaume said the bridge acted like a horizontal chimney and that bone-dry conditions intensified the fire.
“Whatever was inside the bridge if they didn’t fly out or wake up they didn’t make it,” Rheaume said.
The cause of the fire is still being investigated. According Detective Lt. Reg Trayah, they do not believe it was a malicious act and have not found any signs of an accelerant at the scene.
“We don’t have any evidence that somebody was around there that purposely set this fire,” he said.
The bridge was co-owned by the towns of Cornwall and Salisbury and both must have a contract in place for a temporary bridge within 180 days of the incident. It is unclear when a new bridge would go in or what kind of structure it would be.
Bennett says it’s almost impossible to know if and how many bats may have perished in the fire. “Finding a carcass,” she said, “is like finding a needle in a haystack.”
However, because bats sleep during the day, if there were large numbers roosting in the bridge it’s unlikely many of them survived. According to data Bennett collected this summer the majority of the bats were living in the bridge though some had taken up residence in a nearby bat house erected on land owned by The Nature Conservancy.
The first indications of the fire’s impact will be gleaned next summer when Bennett and a handful of volunteers monitor the site. If numbers have gone down, Bennett says, that would obviously be a concern. But she’s hopeful and says the installation of bat houses on Nature Conservancy land next to the bridge provide additional roosting habitat and may prove essential to the survival of the colony.
The Conservancy’s acquisition of more than 600 acres of land throughout the Otter Creek swamps and the conversion of farmland back to its natural state is one of the reasons the area has become so desirable for bats and other wildlife. According to Rose Paul, the Vermont chapter’s director of critical lands and conservation science, when they purchased the land north of the bridge in the early 1960s, about 50 acres, it was primarily used to grow hay and corn. The Conservancy has turned it back into a forested swamp—the state also owns about 100 acres in the area—with mink, otter, muskrats, a variety of birds, insects, and frogs. “It’s a thriving place now,” said Paul.
Since white nose syndrome was first discovered in Vermont in 2007 the little brown bat population has been almost completely decimated. Little brown bats are one of six species in the state that hibernate during the winter, when the disease sets in. The fungus destroys the bats’ skin tissue causing them to burn through their fat stores too quickly. From 2008 to 2010 Bennett says they saw massive population declines. Based on that data they projected that the species would go extinct within 15 years.
However Bennett says the little brown bat population appears to have stabilized at least for now. A small percentage still die each winter but nowhere near what it was just five years ago. The summer colony living in the bridge was in fact increasing.
“The few that remain are precious,” said Paul. “They’re the reserve from which we’re going to build back up our bat populations to numbers we used to have.”
In order for that to happen, data gathered from the swamp road site since 2006 could be crucial. According to Bennett, nobody else in the United States or Canada has records going back that far.
And some of the bats that were first monitored and banded in 2006 have been recaptured as recently as last summer. Bennett says little brown bats can live for 20 to 30 years. She’s kept tabs on this particular colony for 10 years and has held many of the bats in her hands. She knows some from the markings on their wings or ears damaged from frostbite. “It’s like being part of a family legacy,” Bennett says.
Bennett says bats are loyal and that they’ll return to any given site for decades. Next summer she will be watching closely to see if one of most important bat colonies in the state has a future.
