Bucks County's largest bat population has met a grim fate.
Scientists have confirmed that nearly all of the 10,000 bats that have hibernated in an abandoned iron ore mine in Upper Bucks for generations have died.
When Pennsylvania Game Commission Biologist Greg Turner recently visited the Durham mine for the first time in two years, he found total devastation.
The Durham bat mine was once the second largest known bat habitat in Pennsylvania, but this winter only 23 were found alive. Of those, half had clear signs of infection.
Bucks County's bats were wiped out by a disease that has been killing bat colonies across the Northeast at an alarming rate in the last four years.
White nose syndrome causes a white fungus to form around the nose of infected bats. They lose the body fat needed to survive hibernation and ultimately the mammals starve to death during the winter months.
During his visit to Durham's mine on Feb. 21, biologist Turner found three different species of cave bats. Eighteen of the 23 bats were little brown bats. Of those, half of them were crowding at the entrance to the cave or had fungus on their muzzles; both are tell-tale signs of the fatal infection.
“The important thing is that we're still seeing declines at that site,” he said.
In January 2011, biologists first discovered signs that the disease had spread to the bats in the Durham mine, and it was too late to save them.
When Turner and his team of state biologists checked on the Upper Bucks bats in March 2011, they found 180 surviving bats, and half of those had fungus around their muzzles. At that time, scientists held scant hope in the ability of about 50 bats to survive and reproduce in order to sustain the colony.
This winter's sad discovery spells the end for the once thriving colony. For fear of spreading the infection, state biologists won't visit the gated mine tucked deep into a wooded hillside for another two years. Turner expects that when he returns he may only find a few surviving bats.
In Pennsylvania, 98 percent of cave-hibernating bats have died, said Turner.
“Going to places where there used to be tens of thousand bats hibernating, and then going in and seeing only a few bats -- only a few stragglers left -- that's very difficult,” said Turner, who has been documenting the rapid decline of the state's bat population and working with a team of scientists to research how it's spread and experiment with a variety of treatments.
Federal scientists are currently in the process of determining if the six species of cave bats will be included in the endangered species list, said Turner.
Though scientists are still uncertain how the disease is spread, they hypothesize that cave explorers inadvertently picked up fungus spores on clothing and gear while exploring European caves, and then used the same, unwashed items to explore caves in the U.S.
There is reportedly no threat to human health.
Often called the “farmer's friend” because of their diet, bats hibernate each winter and spend the spring and summer months feeding on hundreds of tons of nighttime insects. One bat will consume 900,000 insects per year.
With the significant loss of its largest bat population, it will likely be a buggy summer in Upper and Central Bucks County, Turner estimates.
Scientists have not yet begun to formally study the overall impact of bat deaths on the ecology and farmers' crops, or to track the correlation of the spread of insect-bred diseases like West Nile virus. But biologist Turner notes he has been hearing anecdotally of the increase of summertime insects and an uptick of West Nile and similar infections in parts of the country.