Can bats be repopulated?
By Jeff Zeringue
Bats are an important species in forests; they consume enormous amounts of insects each night.
In Louisiana there are 12 different types of bats, 10 of which have been caught and cataloged by Texas Tech University graduate student Carlos Garcia. However, neither the elusive Yellow bat nor Mexican Free-tailed bat that flies above the forest canopy are what excites him most.
Garcia’s study of bats in Louisiana focuses on the Northern Long-eared bat, the myotis septentrionalis. It is a threatened species in northern areas of the United States because of pseudogymnoascus destructans, a fungus that causes white-nose syndrome.
When the fungus infects the nose of the bat during hibernation, the flying mammal can suffocate. If it wakes long enough to clear its nose, it often expends much of its energy. So as temperatures rise and the bat emerges from hibernation, it lacks the ability to aggressively feed to restore its strength.
So far, the fungus has not been discovered in bats in Louisiana. Up north, however, Northern Long-eared bat populations in some areas have experienced a reduction of 98 percent because of the fungus.
The Northern Long-eared bat, Garcia said he believes, could have been in Louisiana for a long time — it was documented to be in Louisiana in 2003. Although each bat species has its own frequency, vocalization of the Northern Long-eared bat and Southern Long-eared bat are similar. So the Northern Long-eared bat might have been misidentified.
“It (Northern Long-eared bat) has longer ears and a pointier tragus (the inner side of the ear),” Garcia said. “It helps them to echolocate.”
Another subtle difference in the bats is the outer wing of the Southern Long-eared bat connects to its ankle. For the Northern Long-eared bat, the wing connects to the fourth or pinky toe.
Garcia received a permit from the Louisiana Department of Wildlife and Fisheries to capture the bats and set a goal to capture 30. He missed that goal by only one and was able to track 28 of those. He has been in Louisiana for four “bat” seasons — two summers and two winters.
Kisatchie National Forest was the area Garcia used in his study. Emlyn B. Smith, district wildlife biologist for the national forest, said using Kisatchie was an easy choice because its large area of suitable habitat for this species on public lands in Louisiana.
“It is easier to track the bats once telemetry trackers are installed when all the land ownership is the same,” she said.
In March, Garcia and Beth Meyer, who works for Environmental Solutions and Innovations in Washington state but helps in environmental and conservation studies, set up nets to capture bats as they cruised a small stream in the Catahoula District of Kisatchie National Forest. The stream is a good water source from which the bats can drink.
Bats usually begin emerging at dusk, so Garcia and team have their nets in place by sunset. It is a rather tricky business catching a nocturnal animal that uses echolocation to “see.” From a distance, the nets are practically invisible. At sunset, it’s impossible for a person to see, but the light nylon netting does its job as four bats were captured — a Red bat, two Evening bats and, to Garcia’s delight, a Northern Long-eared bat.
The Red bat and Evening bats were cataloged and collected for study, but the Northern Long-eared bat was processed, tagged with a number band and radio transmitter then released. Because of its population decline, the Northern Long-eared bat was listed as threatened in 2015.
The number band is used to make sure the same bat isn’t captured and data repeated. To attach the radio transmitter, the back of the bat just below the head is shaved. Then an adhesive is applied and the transmitter and 4- to 5-inch antenna is affixed.
“As the bat’s hair regrows, the transmitter is loosened then just drops off,” Garcia said.
The transmitters usually last less than a week, so Garcia and his helpers track the bats during daylight hours right after they are released.
“They’re not very picky where they sleep,” Garcia said.
Northern Long-eared bats are opportunists, he said. In the forests of Louisiana, they find shelter in cavities of trees — living or dead — under loose bark or even under branches.
With warmer temperatures in the South, bats have shorter periods of slumber. In northern regions, the bats hibernate for longer periods in caves and rock crevices in groups to stay warm. The conditions are ideal for the fungus to grow.
In his research, Garcia said, he has searched under bridges and in culverts as possible sleeping sites for the nocturnal creatures, but after two years in Louisiana, he has yet to find any Northern Long-eared bats using those places.
Another advantage in Louisiana is warmer winters, Garcia said. Bats here do not hibernate. They go into a state called torpor, a sort of lethargy or mini-hibernation, when temperatures drop. Although the fungus that causes white-nose syndrome has not been found in Louisiana, Garcia hypothesized that because cold periods are short-lived, the bats possibly could clear away a fungus before becoming a threat.
“Whenever the temperatures warm up, their metabolism cranks up and they go to feed,” he said.
The population of the Northern Long-eared bat in Louisiana is uncertain, Garcia said. Determining population would take a different study across the state.
“I can’t say there’s a healthy population (in Louisiana) because there needs to be a longer study regarding the bat in general,” he said. “I don’t think this is a good sample size.”
He said based on the bats he has been able to catch — 29 — it would not be enough to calculate the population in Kisatchie, much less the entire state.
Also, it’s difficult to say how good the bats are at evading the nets. As an example, he uses the Yellow bat that is known to be in Louisiana, but have eluded capture.
As for the Northern Long-eared bat, Louisiana could play an important role in the future, the scientist said. If populations in other areas of the United States continue to dwindle, the species here could be captured and relocated to repopulate the regions where the bats were once natives.
In the meantime, other studies are possible, Garcia said. Little is understood about whether there are certain types of trees the bat prefers or what kind of habitat it favors.
“There’s still a lot more to study about them.”