Photo courtesy of Louisiana Department of Wildlife and Fisheries.
A Big Brown Bat, photographed roosting in a culvert.
On a recent summer afternoon, I found myself on my hands and knees looking at what appeared to be a tiny, sneering Brazilian Free-tailed bat. It was all a part of my mission to learn more about Louisiana’s twelve species of bats, and about the Louisiana Department of Wildlife and Fisheries’ bat monitoring program.
These flying mammals are an integral part of our environment and provide critical ecosystem services. And they face many threats. One major threat facing bats in Louisiana is habitat alterations, including degradation, fragmentation, and destruction. When a bat’s habitat is altered or lost, the bat must move to a lower-quality habitat for roosting and foraging. An even more urgent threat for our region’s bats, however, is the deadly disease known as White-nose Syndrome.
These flying mammals are an integral part of our environment and provide critical ecosystem services. And they face many threats.
Pseudogymnascus destructans or Pd for short, is a fungal infection that causes the disease known as White-nose Syndrome. A cold loving pathogen, Pd infects bats during hibernation when their bodies’ temperature decreases. After the infection invades a bat, its wing membranes start to erode, white cotton-like fungus grows on its muzzle and wing membrane, and dehydration occurs. The pathogen awakens the bats from hibernation, using up necessary energy and depleting fat reserves. Thus far, over six million bats have died from the disease since it was detected in Albany, New York in 2006.
Photo courtesy of the writer.
Big Brown and Brazilian Free-Tailed bats share a roosting spot under a bridge.
Over the past fifteen years, the disease has been identified in thirty-seven states and seven Canadian provinces; the fungus Pd has also been detected without the clinical presentation of White-nose Syndrome’s symptoms in three additional states.
Researchers have identified twelve bat species with White-nose Syndrome, three of which can be found in Louisiana; the fungus has been detected without symptoms in eight additional species, four of which can be found in Louisiana. While White-nose Syndrome has been confirmed in bat colonies in surrounding states—including Arkansas and Texas—Louisiana has yet to have a documented case of either the fungus or the disease. And the Louisiana Department of Wildlife and Fisheries would like to keep it that way.
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To ensure that the region’s population remains healthy, LDWF Wildlife Health and Disease Surveillance Program collects information on local bat populations, colony size, and locations, which allows LDWF to effectively monitor the potential spread of Pd. To determine if the fungus is in a colony, LDWF biologists take swabs from the wing membrane and muzzles of a number of bats for testing. All LDWF biologists involved in collecting these samples must be vaccinated against rabies prior to entering a bat colony.
Photo courtesy of Louisiana Department of Wildlife and Fisheries.
A Southeastern Myotis Bat photographed roosting in a culvert.
While Louisiana’s bat population seems to be doing well, Dr. Jim LaCour, LDWF State Wildlife Veterinarian and Wildlife Health and Disease Surveillance Monitoring Program Manager, said any significant reduction in the overall population would be detrimental to the state’s ecosystems. Bats play a critical role in our environment, aiding in maintaining genetic diversity in plantlife and in forest regeneration through pollen and seed dispersal. Mostly insectivores, bats also provide the service of controlling our insect populations, feeding on agricultural pests and mosquitos. In all, bats across the country eat hundreds to thousands of airborne insects an hour and save the U.S. Agricultural Industry over $3.7 billion annually.
Dr. LaCour explained that bat migration in Louisiana is largely a mystery, even to scientists, because so many of the species are small and hard to outfit with transmitters, thus their movements go mostly undetected. They do know that in Louisiana, bats breed in the fall, prior to their winter hibernation.
The LDWF bat monitoring program is conducted during the winter and summer seasons. To get up close and personal with the monitoring program, I met Brianna Upton—a technician with the LDWF Wildlife Health and Disease Surveillance Program—one evening in Denham Springs to participate in a sixteen-mile acoustic route that records bat calls if they are in the route area.
Bats are nocturnal creatures, and their peak feeding time occurs in the evenings when they emerge. Bats use echolocation to locate prey by bouncing sound waves off of objects to determine their distance. These high-pitched sounds are difficult, sometimes impossible, for the average human ear to detect.
The LDWF truck is outfitted with a microphone on the roof, which captures sounds through an acoustic recorder inside the truck. A light on the recorder stays red until it picks up a bat call, and then flashes green. Upton drove less than twenty miles an hour to enable the recorder to pick up those high frequency calls. There were a few green flashes along the way. Later, she would put the recorder disk through a computer program to identify bat species. Some of the species that might present themselves on routes such as these include Big Brown, Evening, Free-tailed, and Hoary bats.
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Louisiana’s landscape does not naturally contain caves, so bats in this region tend to congregate in alternative cavities for roosting, including holes in abandoned buildings, attics, and transportation structures like bridges and road culverts.
Occasionally bats will even use these structures as maternity colonies to raise their young. Because mother bats are sensitive to colony disturbance, which could negatively impact the pups, LDWF keeps monitoring during maternity season to a minimum. Nikki Anderson, the LDWF Wildlife Disease Biologist in charge of the bat monitoring program, said LDWF would only allow me to visit a colony once the maternity season was over. Respecting LDWF’s sensitivity to these new moms and keeping my expectations low, I ventured out on a survey a few weeks after the monitoring season ended with LDWF bat monitoring program volunteer-turned-employee, Katherine Gividen.
Our destinations—sites where Gividen thought bat colonies were likely to be roosting—were not always immediately visible to the naked eye, and we only found two of them after traipsing through the trees and down a hill, knocking out overgrown shrubs and vegetation.
We discovered bat species in three of the four locations. Going into two large culverts in a dryish-creek bed, Gividen found a Tricolored bat. At the opposite end, we noticed a Big Brown bat as well.
At the final stop, we crawled under a bridge and located several bats snuggled together, which was when one of the bats seemed to pull his lips back, revealing a sharp set of teeth
At the second stop, water surrounded the only entrance to the culvert, which sloped downhill at an angle. In other words: there was no light at the end of this tunnel. After wading into water, Gividen inspected the entrance and said that she could hear bats. Leaving my claustrophobia outside, I joined her, entering on hands and knees. Inside at the upper end, we found a large colony of bats.
At the final stop, we crawled under a bridge and located several bats snuggled together, which was when one of the bats seemed to pull his lips back, revealing a sharp set of teeth.
Seeing these furry, reclusive skeeter-eaters in their roosting spots provided an intriguing glimpse of the under-appreciated ecosystem crusaders. If you have a smidgen of interest in helping to ensure that the Louisiana population stays healthy and happy, LDWF could use your help. They will supply you with all equipment and training.
For more information, contact Nikki Anderson at Louisiana Department of Wildlife Fisheries, ldwfwildlifehealth@wlf.la.gov or (225) 765-5030.
