Insect-eating bats likely save the U.S. agricultural industry at least $3 billion per year in pest control, according to an analysis published in this week’s Science magazine’s “Policy Forum.”
According to Paul Cryan, a U.S. Geological Survey (USGS) research scientist who specializes in small mammals and was one of the authors of the report, bat species have diversified to live in almost any climate on a wide variety of foods.
“In the temperate zones, bats have become the masters of feeding on night flying insects,” Cryan said. “Insect-eating bats in the U.S. are major predators of night-flying insects and many of those insects also damage or feed on our crops.”
Though the study focused on U.S. agriculture, the study’s authors are from wide-ranging institutions such as the University of Pretoria in South Africa, USGS, University of Tennessee and Boston University. The savings that insectivorous (insect-eating) bats provide to the U.S. alone range from $3.7 billion to $57 billion.
Due to the close link between the health of the bat population and the massive U.S. agricultural industry, the study’s authors warn that threats to bat survival, such as the disease White Nose Syndrome (WNS), could adversely affect the nation’s farms.
“Farmers and foresters have always had bats working for them, whether they knew it or not,” Cryan said. “That isn’t something that can be assumed anymore now that WNS has emerged.”
WNS is caused by a cold-loving fungus that infects bats as they hibernate in caves in the winter. Bats infected with this fungus have low body fat (a dangerous condition during winter hibernation) and display unusual behavior such as flying during the day and in seasons in which the insects they feed upon are in low supply.
“WNS is huge in its effect,” said Janet Foley, an associate professor in the UC Davis School of Veterinary Medicine and vector-borne disease epidemiologist. “It can kill 70 to 90 percent of all bats infected, can wipe out populations and could lead to species extinctions.”
Foley and her colleagues decided to study infectious diseases in bats because the cause of the WNS epidemic is so difficult to determine. Her paper is included with the research published by Cryan in this week’s Science. Though WNS currently only affects bats in the eastern U.S., there is concern that it could easily spread to other populations.
“Since bats fly, sometimes quite far, obviously they are likely to transmit [WNS],” Foley said. “But it’s also possible that the fungus is already present in some caves and just hasn’t caused disease yet.”
Bats are highly important transmitters of disease both among their own species and to other species. Bats can be infected with diseases like rabies and henipaviruses, which cause fever, nausea and seizures.
“It’s not clear that any of these hurt the bats, but bats are reservoirs, so there’s something about bats and the diseases they maintain that deserves study,” Foley said.
As these diseases affect what Cryan calls an “absolutely free pest control service,” the agricultural industry is highly interested in maintaining bat populations at a healthy level. In their respective papers the authors suggest some methods of helping bats.
Foley suggested in her report that people continue to “support research into causation, transmission, possible treatment and vaccination,” as well as giving money to wildlife conservation habitats.
The reports also tell the hard truth about the many difficult threats facing bats.
“At the moment there are no easy answers,” Cryan said.
AMY STEWART can be reached at science@theaggie.org.
