ACROSS MISSISSIPPI — Bats, an organic method of pest control, may become rare in the United States and Canada.
The primary predators of night-flying insects, bats reduce the need for chemical pesticides and save the agriculture industry an estimated $3 billion per year in pest-control costs. But bat populations across the Eastern United States are decreasing at alarming rates because of a fungus thought to be imported from Europe.
“Bats in 19 states and four Canadian provinces are dying at high rates because of a cold-loving fungus, Geomyces destructans,” said Dr. Nicole Hodges, research associate with Mississippi State University’s Forest and Wildlife Research Center. “The fungus results in a disease called white-nose syndrome, and it’s decimating our bat colonies.”
The fungus has been found in Alabama but has not yet been discovered in Mississippi, she said.
Because the fungus will grow only between 33 and 59 degrees Fahrenheit, some scientists think that Mississippi is not in danger, Hodges said.
“I feel that the reason we have not seen white-nose syndrome in Mississippi yet is because our temperatures are not in that range for an extended period of time,” Hodges said. “But I have recorded temperatures in culverts, where bats often roost, that are within the range hospitable to the fungus.”
The state’s agriculture industry is expected to feel the financial impact if bat populations decrease.
“I imagine it would have a huge impact if growers in the Delta area had to compensate for the loss of pest control provided by bats,” said Kathy Shelton, a biologist with the Mississippi Department of Wildlife, Fisheries and Parks.
Hodges and Shelton work with scientists across the state to monitor bat populations and watch for any sign that the fungus causing white-nose syndrome has moved into the state. Their work takes them to some unusual places.
Mississippi has a limited number of caves but does have many bridges and drainage culverts, where bats can roost during the day. From the outside, these culverts often resemble naturally occurring caves.
Undisturbed caves and culverts are especially important to bats when it gets cold, because they go into a deep sleep or winter dormancy similar to hibernation. They cannot wake quickly, which puts them at risk of falling when disturbed.
Hodges said veterinarians and biologists are still trying to determine exactly how bats are affected by the white, powdery fungus that grows on their faces, ears and wings.
“It is suspected that the fungus causes discomfort to the bats, almost like it makes them itch,” Hodges said.
Bats with the fungus wake up from winter dormancy, which causes them to exhaust energy reserves that are critical for overwinter survival.
“The bats basically end up starving to death,” she said.
The fungus was first documented in caves in New York in 2006, but it has spread rapidly. The mortality rate in infected colonies is 90 to 95 percent. Some studies report mortality rates as high as 100 percent in localized populations of bats.
Hodges said this situation could reduce numbers of endangered bat species, such as Indiana and Gray bats, to levels that may lead to extinction.
The disease is not dangerous to humans. Bats contract the disease from other bats or the environment. Currently, there are no known methods of controlling the fungus without harming the entire cave ecosystem.
As part of efforts to protect bats, Hodges stressed the need for people to move beyond the myths and misconceptions about bats.
“Mississippi doesn’t have vampire bats. The bats here eat insects. In many places, they pollinate fruits such as bananas, mangoes and guavas. They also disperse seeds,” Hodges said. “Bats are an important part of the ecosystem.”
Shelton said it is extremely important that people stay out of drainage culverts.
“They’re unsafe places to play, and people will disturb roosting bats, especially those in winter dormancy, which can lead to unusually high mortality in the bat colony,” Shelton said. “We encourage people to appreciate bats from afar. They’re living animals, not toys for target practice,” she said.