Fort Knox, a U.S. military installation located near Louisville, Kentucky, and famous for storing the nation’s gold bullion, has two of the largest known maternity colonies of federally endangered Indiana bats within the range of the species and the largest in Kentucky. On the same night, officials documented 451 and 478 Indiana bats emerging from two separate trees, both are records for this species. The first maternity colony of Indiana bats on Fort Knox (approximately 150 individuals) was discovered in 1999. The total number of Indiana bats in existence has declined due to white-nose syndrome, a devastating wildlife disease; a reduction and contamination of their insect food supply due to pesticide usage and disturbances by humans during the bats’ winter hibernation in caves and mines. During hibernation, bats cluster in groups of up to 500 per square foot, which means a single event can destroy a large number of bats.
Fort Knox, a U.S. military installation located near Louisville, Kentucky, and famous for storing the nation’s gold bullion, has two of the largest known maternity colonies of federally endangered Indiana bats within the range of the species and the largest in Kentucky. On the same night, officials documented 451 and 478 Indiana bats emerging from two separate trees, both are records for this species. The first maternity colony of Indiana bats on Fort Knox (approximately 150 individuals) was discovered in 1999. The total number of Indiana bats in existence has declined due to white-nose syndrome, a devastating wildlife disease; a reduction and contamination of their insect food supply due to pesticide usage and disturbances by humans during the bats’ winter hibernation in caves and mines. During hibernation, bats cluster in groups of up to 500 per square foot, which means a single event can destroy a large number of bats.
Fort Knox established the 1,458-acre Indiana Bat Management Area (IBMA) to manage and increase the population of Indiana bats as mitigation for one of its range construction projects, but also used it for a KY EXCEL project. KY EXCEL is Kentucky’s voluntary environmental leadership program. Management activities in the IBMA include wetland monitoring/management, selective girdling of trees to create roosting sites, invasive species removal and timber stand improvement operations to provide a quality foraging habitat.
In the summer, Indiana bats roost, give birth and rear their young under slabs of loose bark of primarily dead or dying trees. Weighing only a fourth of an ounce, or about the weight of three pennies, Indiana bats are tiny, but in flight have a wingspan of 9 to 11 inches. Indiana bats eat a variety of flying insects found along rivers or lakes, benefiting humans by feeding on insects that are considered pests or otherwise harmful to people, such as mosquitoes. An amazing fact about Indiana bats is that they eat up to half their body weight in insects each night, and a colony of bats can consume thousands of insects per night.
The maternity colonies at Fort Knox have been monitored each year since their discoveries through the use of mist netting, radio telemetry and acoustical surveys. In 2006, Fort Knox initiated a project to augment summer roosting habitat through the use of installing artificial bark on standing dead trees in the IBMA near known maternity trees.
Over the course of the artificial bark project, several roost trees fell due to wind or natural deterioration. In 2012, in an attempt to create longer-lasting roosting structures, six power poles, pressure-treated only at the bottom to eliminate possible negative effects to bats, were placed in the IBMA and outfitted with artificial bark. Of the six structures, five had evidence of bat use within 60 days and all showed use within 85 days.
Jimmy Watkins, wildlife biologist at the military base said that approximately $50,000 has been spent on the project. Though Fort Knox will not receive any economic value from the bat roosting project, the benefit to the continuation of the species and the environment is significant.
“The main challenge we encountered in this project was getting equipment to the site to erect the poles,” says Watkins. “Basically, it required the same equipment as power/communication companies use to put up utility poles. Indiana bats occur in wooded areas in summer, so it can be challenging to get the roosting structures where they need to be. I would recommend a partnership with a utility/communication company, or at least a cost-share conservation program with them. Our contractor worked out all those details with Louisville Gas & Electric.”
“Bats began using the artificial bark almost immediately,” says Watkins. “As many as 451 bats were observed emerging from one of the artificial structures. Mist netting confirmed pregnant Indiana bats, along with little brown bats and one northern long-eared bat, indicating use as a maternity site.”
Artificial roost structures will last many years providing quality roosting sites for Indiana bats and other species of tree-roosting bats. They also offer a certain amount of flexibility due to the fact they can be placed on the landscape in areas that may reduce potential conflicts with military training, which is good for military readiness and for the conservation of bats.
“Artificial roosting structures have provided natural resource managers with an important tool in the management of Indiana bats, as well as other imperiled tree-roosting bats,” says Watkins. “While the use of artificial bark is encouraging, natural roosts are still very important, because Indiana bats switch roosts every 2–3 days during the summer. Research is currently being conducted in the IBMA to refine methods of producing natural roost trees through varying treatments of girdling and chemical injection. Forest management activities are also ongoing to improve foraging habitat. Fort Knox will continue to monitor the artificial roost structures and plans to install them in other areas of the installation where suitable summer Indiana bat maternity habitat exists.”
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Bat image provided by Fort Knox.
