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For as long as anyone can remember, each summer night at dusk the skies over Juniata County, Pa., would come alive, as countless little brown bats fluttered through the mouths of caves and abandoned mines to feed.
About six years ago, that nightly ritual went silent. Thousands of bats, sick with a fungal infection that has now spread throughout much of North America, died off in droves. But a small contingent of 500 or 600 bats has held on, surviving in a Juniata County bat box monitored by state wildlife managers. Understanding what enabled those bats to survive may be key to solving the mystery of the infection, called white-nose syndrome, and saving threatened bat populations throughout the country.
Bucknell University is uniquely equipped to tackle that investigation, and the U.S. Fish and Wildlife Service has awarded a pair of Bucknell investigators a nearly $350,000 grant to take on the challenge.
"The remnant populations of bats left throughout the northeastern United States are the hope for the future of bat populations here, and our ability to understand how natural selection has acted on them is critical," said Professor DeeAnn Reeder, biology, a bat expert and one of two recipients of the grant.
Reeder has been studying white-nose syndrome since it was uncovered in 2006, and led the first federally funded field study of infected North American bats. Thanks in part to her efforts, scientists now have a much clearer understanding of the disease's pathogen, the ominously named fungus Pseudogymnoascus destructans, and the ways it acts upon infected bats. In her latest investigation, Reeder will draw on the expertise of immunologist and biology professor Ken Field to ask how bats like those in Juniata County might survive the epidemic.
"We're not sure if it's something the bats can pass on to their offspring — a genetic component — or if it's an adaptation they've made to the fungus being present that allows them to survive," Field said. "If we find that the bats can mount a protective immune response, we could try to increase that response by vaccinating them. It's not feasible to vaccinate millions of bats in the wild, but we could target endangered species or particularly vulnerable populations."
The disease is quickly rendering more and more bat colonies vulnerable. The first North American bat with white-nose syndrome was discovered in 2006 outside Howe Caverns near Albany, N.Y., and since then the fungus has spread to 25 states and five Canadian provinces. The disease is common throughout Europe and Asia, but doesn't kill off bats there in large numbers.
As Field explains, the white-nose fungus thrives in cold environments, and only negatively impacts bats that hibernate. For reasons not yet known, the infection causes some bats to wake more frequently during hibernation.
"They may arouse two or three times more often than they would without the fungal infection," Field said. "That's enough to deplete their fat reservoirs before they reach the spring, when there's food available to eat."
While most bats survive the first winter after infection, few can outlast the second, Field said, and the smallest bats are the most vulnerable. The common little brown bat has been particularly hard hit, with infected colonies losing an average of 90 to 95 percent of their members, but even heftier species such as the big brown bat have been significantly impacted, losing 40 to 60 percent in infected populations. Considering that bats make up 20 percent of all mammals by species, and that each bat can consume twice its body weight in insects in a single night of feeding, it isn't hard to image the disease having a massive ecological impact.
"We do not have accurate estimates of either past or current insect populations," Reeder said. "However, bats are major insect predators and perform significant ecosystem services. Some have predicted that the insecticide value of bats is in the millions of dollars."
To determine what has allowed remaining Pennsylvania bats to survive, the researchers will perform both genetic expression analysis and behavioral observation on three groups of bats they will collect over the next two years.
The first set will be survivors of a Pennsylvania colony that has already experienced a massive die-off. The second will come from Michigan, which saw its first white-nose infections last year, and the third group will come from Montana, where the disease has not yet penetrated bat populations. The researchers will travel to each location to collect bats for the study, using nets to ensnare bats as they exit cave mouths and diving deep underground to capture them by hand.
They will bring the creatures back to Bucknell's Robert L. Rooke Science Center, which is uniquely equipped for studying bats. Tucked behind three locked but otherwise innocuous-looking doors inside Rooke are the University's bat caves — light and temperature controlled rooms containing flight cages roughly 6 feet high by 6 feet wide and 10 to 20 feet long — which allow the bats to fly freely and provide places to sleep. During winter months, the bats will be moved into 10 hibernation chambers. Custom built with input from Reeder, the chambers simulate the low temperature and high humidity of a cave in winter and allow the researchers to observe bat activity with infrared cameras.
Bucknell students will play important roles in monitoring bat behavior in both environments. They will also aid the project by performing gene expression analyses, hand-feeding the animals (only students vaccinated for rabies are allowed to handle bats) and even accompanying their professors on field expeditions to caves.
"Bucknell is unique in that students are not only welcomed, but encouraged, to join research labs as early as their freshman year," said Beth Rogers, a summer research intern who hopes to accompany Field and Reeder to Michigan. "Undergraduates are valued as scientists and given the opportunity to do real research beside their professors."
Reeder will also be providing bat tissue samples to researchers at the University of Akron and Ohio State University, who will study whether mycoviruses, or viruses that infect fungi, can fight the white-nose fungus. She is named as a collaborator on that project, which received a Fish and Wildlife Service grant totaling nearly $225,000.
She and Field hope the results of theirs and other projects will lead to an effective way to combat white-nose syndrome, and bring life back to the evening skies.
"We have made enormous strides in understanding white-nose syndrome from the perspective of both the host and the pathogen," Reeder said. "Now we need to take the information that we have learned and make wise management decisions for remaining bats."