ARNOLD AIR FORCE BASE, Tenn. -- Nine species of bats are known to occur at Arnold Air Force Base.
They range in size from the tiny tricolored bat, weighing only 4 to 8 grams, to the hoary bat weighing in at 25 grams. Regardless of their size, however, all of these bats eat insects. Their appetite for insects benefits everyone from reducing the bothersome pests in our backyards to saving farmers millions of dollars in crop damage and pesticide costs.
Three of the bat species at Arnold AFB are currently listed under the Endangered Species Act, or ESA - the gray bat (endangered), the Indiana bat (endangered) and the northern long-eared bat (threatened). Gray and Indiana bats have been listed for many years due to declining numbers caused mostly by habitat loss and degradation. However, the northern long-eared bat’s recent listing was due to declines caused by white-nose syndrome, or WNS, which is a disease caused by a fungal pathogen.
The fungus was accidentally introduced into a cave in the United States around 2006. It spread rapidly and survives in caves where it attacks bats while they are in winter hibernation.
Winter mortality can result as the infection causes bats to wake too frequently and burn all their fat reserves before emerging in the spring. Bats that survive show no signs of immunity and are re-infected when they return to caves the following winter. All species of cave-dwelling bats in the east have shown signs of infection.
In fact, six of nine bat species found on Arnold AFB are known to be susceptible to WNS – gray bat, Indiana bat, little brown bat, northern long-eared bat, tricolored bat and the big brown bat. All of these species roost in caves during the winter where they are vulnerable to WNS. The little brown bat and tricolored bat are currently being considered for ESA listing due to precipitous declines from WNS. Three bats on Arnold AFB – red, evening and hoary bats – use forests year-round and are not susceptible to WNS.
Arnold AFB has been conducting bat research and conservation for more than 20 years with studies ranging from annual monitoring to radio telemetry tracking from airplanes.
Annual monitoring includes capturing and marking bats with uniquely numbered bands in the summer, as well as operating acoustic recording stations year-round that record bat’s echolocation calls. Included in their ultrasonic repertoire, bats have certain call sequences that can be identified to species. Telemetry studies have been used to track bats foraging on base to identify important habit, find roost trees and even identify migration routes.
This work has contributed to the knowledge needed to conserve bats, and not just at the base level. For example, all results from acoustic monitoring are uploaded to a national database used to evaluate species trends.
Bats banded by Arnold AFB have been recaptured in caves from McMinnville to as far away as Kentucky and Alabama. A tricolored bat that was being tracked left its winter cave nearby and, instead of making the easy jump to Arnold AFB, flew to an Atlanta suburb and roosted in someone’s front yard. Gray bats captured while foraging for insects on base made nightly commutes of up to 60 km to spend the daylight hours in their summer caves.
Unfortunately, the long-term data set accumulated through years of monitoring has also documented the severe declines resulting from WNS. Arnold AFB has documented post-WNS declines of tricolored bats by 85 percent, little brown bats by 90 percent and northern long-eared bats by 96 percent. On a brighter note, gray bat captures have increased by 102 percent.
Other important contributions Arnold AFB personnel have made involve cooperative efforts with partners including the Tennessee Wildlife Resources Agency, The Nature Conservancy, U.S. Fish and Wildlife Service and others. With the wide-ranging habits of some species – not to mention the 10,000 caves in Tennessee – cooperation and communication between agencies is important to accomplish big tasks that no one entity can do alone.
The willingness to be a cooperative partner also benefited the base when negotiating a programmatic agreement with the USFWS that limits restrictions due to ESA-listed bat species that could hamper projects from forestry to testing. As more species are likely to be listed due to WNS, continued good communication and willingness to be a good partner are increasingly important to support the mission.