Bat man's mission

GRAND TOWER, Ill. -- The stillness of a humid, late-spring day in the Oakwood Bottoms Greentree Reservoir just north of Grand Tower is disturbed by the unnatural rustling of grass and the crunch of dead brush beneath steel-belted radials. A caravan of four four-wheel-drive trucks beats its own path through 5-foot-tall grass atop a small levee. Brake lights flash, and the rumble of engines ceases beside a stagnant, mosquito-infested drainage ditch. Dr. Tim Carter steps out of his truck and pauses to listen.

"Somebody's here," he announces, pointing to two bottle-rocket-shaped structures standing over 12 feet tall in the forest across the ditch.

As the natural whispers of the forest settle back over the brief disturbance of man and machine, a quiet squeaking chorus grows, emanating from the two boxes that sit atop the poles. Carter and his team of five biologists are relieved and comforted by this sound. It means there's a good chance the friends they've come to visit are home.

Carter is a bat biologist who works in the zoology department at Southern Illinois University. He and his team have come to check on a maternity colony of bats that have been roosting in the two boxes, or bat houses, for the past four years. In particular, they've come to see how the endangered Indiana bat, which is all too familiar with the disturbance of man, is coming along in the height of its reproductive cycle.

Indiana bats once were plentiful in the eastern and middle parts of the nation. So much so that one cave might hold millions of hibernating Indiana bats during winter. But the species of small bats became endangered in the 1960s. According to a report by the National Biological Service, by 1993 there were only 347,890 Indiana bats in the country.

Carter jokes that bats have a poor public relations agent, since many people are frightened by the myths of the bat attacking humans, sucking their blood and laying eggs in their hair. His fondness for the flying mammals makes him concerned about their well-being, but he also values them for the natural purpose they serve as insect-eating links of the food chain.

"They are a natural pest control," Carter says, swatting at a mosquito on his arm. "I'd hate to think about what it'd be like without them."

A place to live

Carter said the reason for the Indiana bats' population decline is a common problem for all bats: the loss of places in which the bats can hibernate undisturbed by humans. A U.S. Fish and Wildlife Service report states that 87 percent of the known population winters in only seven caves and mines in Missouri, Indiana, Illinois and Kentucky.

Hibernating bats run on such a tight body fuel storage budget that just disturbing a bat from its hibernation could kill it. Caves often are disturbed, intentionally and unintentionally, by vandals, explorers and tourists.

"Bats only live in caves and mines in the winter," Carter says, dispelling another rumor about his friends as he applies a healthy dose of insect repellent.

Indiana bats mate in the fall, but undergo delayed fertilization. The female stores the viable sperm through hibernation, then fertilizes her egg upon awakening in the spring. In the early summer, they roost in the woods, under the loose bark of dead trees, or in bat houses installed in the woods to offer an alternative birthplace if dead trees are in short supply. Over the past four years they have come this particular spot to feed on the bounty of insects provided by the water in the ditch and to give birth. The latter, of course, is why Carter and company are here.

"Nothing matters if they're not having young," Carter exclaims as he pulls out the folded up "bat trap," a homemade bundle of duct tape and plastic. The Indiana bat typically gives birth in early June, which is why Carter has brought his group here in late May. It's easier to catch, identify and count pregnant, mouse-sized mothers than it is to do so with inch-long babies.

Another of the Indiana bats' handful of problems is its inefficient reproduction rate. Whereas the mouse -- another mammal roughly the size of the Indiana bat -- can have up to three litters of six to eight young each year, the Indiana bat females can only have one offspring a year.

Over the past three years, Carter said, 80 to 90 percent of the Indiana bats he examined were pregnant. This year, he has taken a step to further ensure the accuracy of his count of pregnant bats. Rather than just eyeballing the bat belly sizes, he has invited along veterinarian radiologist Mike Muhlbauer and his $30,000 portable sonogram machine. The box, resembling an early1980s word processor, is hooked up to a portable generator on the back of one of the trucks. Carter hopes it will be able to "take pictures" inside the bats to provide a more accurate count.

The bat trap

Now, the team congregates around the bat trap, a contraption consisting of clear sheet plastic wrapped and duct-taped around a tall rectangular box frame of PVC pipe. It resembles the scabbard of some gigantic saber and it is now assembled around the pole of one of the bat houses. Like a scabbard, the tall box of the trap is open at the top and funneled at the bottom. The funnel leads to a long sleeve of plastic that extends outward from the bottom.

The scientists lift the trap up on the pole, as if trying sheath the pole like a blade up to the handle, represented by the house on top. They lift until the top of the trap covers the hilt, or entrance, at the base of the 3-foot tall house. Then two of Carter's colleagues start striking the post, causing the entire house to jostle and rock. A few bats escape to the air through a tiny hole in the top of the trap. But gradually, little black and brown bundles fall from the house into the trap and funnel down into a pillowcase at the end of the sleeve.

As he monitors the yield of fur and wings sliding down the plastic trap, Carter and company begin to suspect an alarming trend is continuing. The first summer after the bat houses were installed four years ago, Carter noticed a different species -- the much more common little brown bat -- roosting among the Indiana bats. Four years ago, he counted one little brown bat among 34 Indiana bats. The next year it was 60 Indiana bats to 40 little browns. Last year, the little browns finally outnumbered Indiana bats 70 to 30.

The little brown bat is similar to the Indiana bat in size and appearance, but is distinguishable by the trained eye as having lighter fur to contrast with darker wings. As a series of light pelts tumbles into the pillow case, Carter's crew is not optimistic.

Some members of Carter's crew are concerned that little brown bats may be competitively displacing the Indiana bats in the area. When Carter first came to this area, before the bat houses were here, there were no little brown bats. That means the houses may have brought them here. Since the little browns are more apt to roost in man-made structures like attics, it may also mean they have simply displaced the Indiana from the houses and that Indiana bats are roosting elsewhere in the area.

Sonogram check

Back at the sonogram site on Carter's tailgate, members of the group smile at the first bat he pulls from the dark blue pillowcase: an Indiana. He spreads the bat's 9-ounce body with his fingers to expose the belly for Muhlbauer to probe with his sonic wand. This one's pregnant.

But after a few more pulls from the bat grab bag, the initial optimism on Carter's face has been replaced by a sarcastic grin of skepticism. The good news: The next 34 bats pulled out of the first house were pregnant. The bad: All were little browns.

"We might have a problem here," Carter says as they take the trap back across the ditch to the second house.

At evening's end, 86 bats were caught from the two houses. Only five were Indiana, but at least all of them were pregnant.

Carter and wildlife biologist Steve Widowski with the U.S. Forest Service think panicking about the displacement of the Indiana bats is premature. They say the Indiana bats can have a roosting radius of up to 450 miles, so the bats just may not have been there at the same time the scientists were. They also say it is in the nature of the endangered bat to jump roosts occasionally. Or perhaps the Indiana bats were there, just not in the houses. Factoring in the small sample size, Carter says there simply isn't enough data, and no conclusion can be reached.

As the sun sets and the mosquitoes come out in full force, the increased volume of screeching coming from the three pillowcases full of bats signals that it is feeding time. Carter and his team open the tops of the cases, allowing the bats to fly forth. Noticeably dejected, the team members climb into their trucks and drives out of the bottoms, hoping their searches of other Indiana bat roosts in the area will produce more uplifting results.

trehagen@semissourian.com

335-6611, extension 137