Hurricanes and Halloween: Florida bats on mosquito-feeding frenzy

October 27, 2004

GAINESVILLE, Fla. — This Halloween, there are lots of treats out there for hungry bats.

After four back-to-back hurricanes that soaked the Sunshine State and caused mosquito populations to explode, bats are now on a feeding frenzy like never before, University of Florida wildlife experts say.

Florida’s 16 kinds of bats are all insect eaters, gobbling up midges, black flies and lots of mosquitoes. Since all of these insects depend on slow-moving or standing water for reproduction, hurricane rains and floods created lots of new breeding areas for them.

Bats look for swarms of insects such as flies or midges because it’s more efficient to feed in a densely populated area than to look for single insects, said Mark Hostetler, an assistant professor of wildlife ecology and conservation with UF’s Institute of Food and Agricultural Sciences, or UF/IFAS.

“Bats are opportunistic and when there are a lot of mosquitoes, bats will eat mosquitoes. Little brown bats are especially fond of soft-bodied insects like mosquitoes,” he said.

A single bat can swallow 600 to 1,000 mosquitoes an hour, depending on the bat species. An individual bat feeds for an hour or so at dusk and retreats to its home site to rest. A second feeding may take place near dawn. With about 100 small brown bats in a typical single colony, a lot of mosquitoes can disappear in a single night.

“There’s lots of food out there for bats now,” Hostetler said. “If the bats can find homes for over wintering, their young will be born, assuring us of more insect-eating bats in spring and summer.”

However, one should not think that bats, by themselves, control mosquitoes, Hostetler said. “A bat colony can eat thousands of mosquitoes, but mosquito populations are measured in millions. Plus, bats primarily feed on larger-bodied insects such as moths and beetles. Thus, even with a colony of bats nearby, one may still feel mosquitoes biting.”

Bats like to feed in newly opened areas in woodlands, and areas with newly downed trees may see more bat activity than usual, he said.

While the storms have created ideal conditions for mosquito breeding, they also have destroyed some important bat habitats such as attics, chimneys and hollow trees, said Ken Gioeli, UF/IFAS St. Lucie County extension agent in Fort Pierce. In fact, the loss of habitat may affect bat populations in the long term.

“I made some preliminary bat-detecting excursions after Hurricane Jeanne, and I noticed a significant decline in the bat population, but those that are left are taking advantage of the mosquito population explosion,” Gioeli said.

He said homeowners can help alleviate the loss of habitat trees by putting up bat houses. A small bat house can accommodate 75 to 100 little brown bats. The chances of occupancy are higher if the house is oriented so one side can be warmed by the sun. The UF/IFAS extension service, which has offices in all 67 Florida counties, has bat house plans available. Bat houses are also available at birdseed retailers.

“Some mosquito species have been associated with viral diseases such as eastern equine encephalitis, West Nile virus and St. Louis encephalitis,” Gioeli said. “They are a major pest problem for people and animals, and when you get right down to it, people just don’t like serving as snack food for mosquitoes.”