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Published July 28, 2008, 12:00 AM

THE BATMAN OF SDSU: Professor says bats eat mosquitoes, but repellents should be used, too

BROOKINGS, S.D. -- Scott Pedersen was a big fan of bats, long before the current blockbuster movie hit the screens, or the last one and the one before that.

By: Mikkel Pates, Agweek Staff Writer

BROOKINGS, S.D. -- Scott Pedersen was a big fan of bats, long before the current blockbuster movie hit the screens, or the last one and the one before that.

A professor in the South Dakota State University Department of Biology and Microbiology in Brookings, Pedersen is one of the region's foremost experts on the furry, nocturnal, flying mammals that help kill mosquitoes, which can carry West Nile disease and other maladies.

In South Dakota, interest in bats took off about seven years ago as the incidences of West Nile virus started coming into the region. While some people looked to bats as a potential defense against mosquitoes, some of which carry the potentially deadly disease, others feared the bats more.

Among other thaings Pedersen is a co-chairman of the South Dakota Bat Working Group, whose aim is to educate people about bats. Among the group's accomplishments is publishing a set of 12 educational books that are available to classroom teachers in the state.

"If you teach kids that bats are cool, you're going to have some pretty damn smart kids 20 years from now," he says.

Good (bats) vs. evil (bites)

It's a well-known fact that bats eat huge volumes of mosquitoes.

In a given evening, an individual bat can dispatch 1,000 to 1,500 mosquitoes, using their famed echolocation ability, to create "sound pictures" in their head, helping them pinpoint their quarry on the wing.

"A typical colony of bats is about 20," Pedersen says, adding, "You do the math."

But Pedersen is quick to add that when you do the math -- as impressive as it is -- bats probably won't win the mosquito wars. At the maximum, 20 bats are most effective four months 120 days, times 1,500 -- about 3.6 million mosquitoes in a four-month season.

"When you open up the stomach (of a dead bat) you'll find a huge compaction mosquitoes. It's difficult to count them all," Petersen says.

"There's a lot of mosquitoes being eaten, but there's billions of mosquitoes out there," Pedersen acknowledges. "Bats do have a significant impact, but is it the sort of impact that allows a typical homeowner or farmer to really perceive it? No."

Spraying a repellent or bug killer is probably the answer.

"We hate to see sprays and all that for a bunch of reasons," Pedersen says. "But that's the only way I know to really control mosquitoes. Bats can do their job, but only to the extent that they're full."

There are 12 to 14 species of bats in South Dakota.

The most common bat in North Dakota and South Dakota is the "Big brown" bat, which feeds on a number of targets, including hard shell beetles and moths, say Pederson and Joel Tigner, a private bat biology consultant from Rapid City, S.D.

"All of the bats in this state eat insects," Pedersen says. "Some 'specialize' on moths, but I think it's fair to say they'll eat the most abundant food because it is easy.

The Big brown bat has a body about the size of a human thumb, but a wingspan of 12 to 14 inches. Females are slightly bigger.

Most Big brown bats in the Dakotas migrate -- probably as far as Nebraska or Iowa, but little is known about that. Researchers have tried gluing radio transmitters to their bodies, so they can be tracked.

"The problem is they fly faster than we can drive, legally, and we lose them," Pedersen says.

Again, funds are limited to simply follow bats around.

"There is a very narrow range of temperature and humidity that a bat has to put himself into and stay in suspended animation," he says. "If it's too cold the bat will die."

The Big brown requires temperatures in the high 30s for optimal hibernation.

Another problem with bats staying in North Dakota and South Dakota is that there are sometimes extreme temperature fluctuations in the spring. The bat will emerge from a barn or attic to forage and then die when temperatures dip.

"It's a bad place for bats to spend the winter," he says.

Bats typically have one baby in a year and the baby stays with the mother until she dies.

Bats take babies with them when they fly and "teach the youngsters everything they need to know," he says.

Bats are being encouraged in the Black Hills.

Tigner encourages people to build bat houses in the Black Hills area so that bats can move from homes or structures where they have been excluded.

In Texas, researchers interested in malaria control built bat towers 40 to 50 feet and "inoculated" them with bats. After a couple of generations, the bats would come back to the site. No project like that exists in South Dakota.

Bat roosting houses look like birdhouses with the bottom knocked off, Pedersen says. One of the designs that works best in North Dakota and Minnesota looks like an envelope that is 12 inches deep -- about 2 feet by 1 foot.

"Bats love those," he says.

In the Eastern states, bats seem to prefer boxy-style houses.

"We don't know why," he says.

Bat houses aren't nearly as attractive as buildings and attics it can take up to three years for bats to occupy a house. Pedersen doesn't push the idea of building them, even though there have been built in the Omaha, Neb., area.

Bats can live up to 30 years.

"If your house has a lot of cracks and holes in it, bats will stay there for years. Some live up to 30 years. Why would you move out?"

Warm temperatures encourage maternity and maturation of the pups, Tigner says.

"Why would a self-respecting bat go into a bat house when there's a house where the chimney has pulled away?" he says playfully. "It's warmer and there is aged wood, a nice enclosure for the animal."

Bats and rabies myth

When bat interest involving West Nile took off, so did some of the fears.

"Everybody started contacting local rabies testing centers," says Pedersen, who does the diagnostic work at the SDSU Diagnostic Laboratory.

In fact, Pedersen says, bats seldom get rabies. Skunks, raccoons, dogs and cats and occasionally horses and cows, will get rabies. "But not bats. They're not a 'reservoir' per se."

About one-half of 1 percent of the bat population for North America ever contracts rabies -- far less than skunks and raccoons, Tigner says. Still, he adds, humans should take precautions when handling bats. You don't necessarily have to be bitten to acquire the rabies virus.

"It's always a good idea to put on some sort of a glove to prevent coming into contact," he says. "Visually, you can't look at a bat and say whether it's sick or healthy."

Further, it isn't known whether bats contract West Nile.

"They should, they're a mammal," Pedersen says. "But we've not been able to demonstrate that."

Pedersen says the bat isn't an economic interest in the state.

"My own research is in the Caribbean, on large fruit bats," he says, adding that -- despite his interest -- his main gig at SDSU is in human areas.

He teaches human gross anatomy using a "true cadaver lab for undergraduate students," primarily to nursing students, pharmacy and pre-medicine students. "We're hands-on around here," Pedersen says. "We're the ag school. We put our hand in there and squeeze!

"Between studying bats and having cadavers around, I'm pretty popular around Halloween," he says.