FORT KNOX, Ky. — Wildlife biologists at Fort Knox are beginning to see some big successes in efforts to rescue endangered bats in the area.
Three species of bats in particular — the Indiana, gray and northern long-eared bat — have been the focus of much of their efforts. Biologists admit their work has been an uphill battle in some cases.
“A lot of people look at a forest and just see trees, and they say, ‘Two thumbs up, that’s great,” said Michael Brandenburg, chief of the Natural Resources Branch, Environmental Management Division, at Fort Knox. “As biologists we look at the trees, not just the forest. We look at what might be undesirable for the growth of the forest. We do the same for bats.
“Our objective is an ecologically based approach that seeks to manage for healthy forests that will better support species dependent on forest habitats — particularly in this case, our listed bat species.”
Federal lawmakers established the Endangered Species Act of 1973 to protect animals, flora and fauna from extinction due to the nation’s focus on economic growth at the expense of the environment, according to the U.S. House of Representatives’ “History, Art & Archive” website. President Richard Nixon signed the act into law Dec. 28 that same year.
According to the U.S. Forest Service, Indiana and gray bats have been on the endangered list since before the creation of the act. By 1999, the populations of both species combined were about 800,000, according to Brandenburg.
“That sounds like a lot of bats,” Brandenburg said, “but relative to what their population historically was, they were in trouble.”
The northern long-eared bat, on the other hand, was abundant in the area.
The reasons for any bat species’ population numbers to decrease are varied depending on their mating, social and hibernating habits, but those reasons in the Fort Knox area included the loss of suitable caves for them to dwell.
“They hibernate in caves, and they weren’t able to,” said Brandenburg. “This is because of filling of caves, flooding of caves, and modifications that made it unsuitable for the bats — basically, direct human contact.”
The cave changes were affecting the Indiana and gray bats more severely than others. For instance, the northern long-eared tend to spread out more when hibernating compared with the other two who cluster in large numbers, according to Brandenburg, so that may have been a factor in long-eared bats thriving.
Over time, efforts to improve water quality helped reduce silt and sediment being deposited into creeks, streams and caves, which made the caves more suitable for the bats.
In addition to cave protection, Fort Knox’s management efforts focused on providing more suitable summer habitats through the installation of artificial roosting structures. A chance encounter with a dead tree sparked the idea.
A biologist noticed one night that a dead tree standing within a swampy area of the installation had separated bark clinging to it that formed a pocket near the top. The biologist witnessed bats flying in and out of the pocket. This realization led Fort Knox officials to attempt to replicate it on other trees.
The idea worked. Now, the area is considered home to the largest population of Indiana bats in the nation.
In February 2006, a new threat entered the United States; first detected in upstate New York. Commonly called white-nose syndrome, the cold-loving fungal disease grows on the snouts and wings of infected bats during hibernation, according to the National Forest Service.
“The fungus causes them to wake up because they become dehydrated; their body is trying to fight off the fungus, so they wake up to groom themselves,” said Brandenburg. “It’s a very complicated pathway. What ends up killing the bat is either starvation, dehydration or exposure.”
The constant need to break hibernation to deal with the fungus ends up depleting necessary fat reserves that bats need to hibernate through the winter months, according to the Forest Service. The bats then must eat and drink to replenish the reserves.
“They fly around in the winter and there’s no water to drink,” said Brandenburg, “and no bugs to eat.”
As a result, the biologists have watched once-numerous northern long-eared populations virtually vanish, while Indiana and gray bats have managed to hold on.
Brandenburg said it was once common for biologists to catch long-eared bats in mist nets for banding and research prior to the syndrome. In the last three to four years, they have caught only one. Populations of the species have declined by as much as 90% in many cases, even higher in colder Northeast regions.
“The northern long-eared bat was one of the most ubiquitous bats in North America, and it has really taken it on the chin with the white-nose syndrome,” said Brandenburg.
He dismissed the notion that they simply migrated to other locations.
“They’re dying; many have died because of white-nose,” said Brandenburg. “They’re gone.”
Other species have also been hit hard by the fungus.
“Now, we’re not only looking at the species that we have listed but the potential for the listing of others in the next two to four years,” said Brandenburg.
Catching and tracking bat species has helped the biologists learn a lot about migration, mating and feeding patterns, which has led them to a greater understanding of how bats survive when cave and summer habitat conditions change. The information gathered at Fort Knox is shared with the Kentucky Department of Fish & Wildlife and the U.S. Fish and Wildlife Service to better manage bats in the region.
Brandenburg said their work has led them to a viable solution to the summer roosting issue, through the use of the artificial roosting structures, although not for fighting the virus.
“If we have a couple hundred bats in a tree, it may be comprised of bats coming from multiple different hibernaculum (underground locations used for winter hibernation] that will constitute a summer colony. That’s good from a population standpoint because if a cave floods and kills all the bats in one hibernaculum, it doesn’t wipe out that whole colony,” said Brandenburg. “From a transmission of a fungus that’s detrimental to a population, it’s not good. That’s likely how the white-nose has spread through the whole range of the species in approximately five to seven years.”
Brandenburg said scientists working to try and control the spread of the fungus are having some success—
“… but bats live in a wild environment. You can’t go vaccinate all the bats, and vaccinations are for viruses,” said Brandenburg. “Fungi are difficult pathogens to try and deal with, especially in wild populations.”
While others continue to battle white-nose, Brandenburg and his team have devoted their efforts to developing better tree roosting habitats for the bat species that remain. They began their efforts by placing shingles on existing dead trees, but winds and rain would soon blow them down, or the tree would fall.
Now, they use recycled utility poles upon which they mount bark-like artificial caps at the top. These poles are providing a much more stable home for the bats.
Strategic placement of the structures also allows biologists to more easily track and monitor the bats. Their efforts have caught the attention of other locations as biologists are beginning to adopt the same techniques.
“We have three colonies [of Indiana bats] that we’ve documented on the installation. Two of those, at least, are the largest known for the species,” said Brandenburg. “It’s good to know that we are doing something positive to preserve our bats.”
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