Census Takes Look at How Bats Are Faring : Ecology: Creatures are under environmental stress, and the data will one day help the mammals to thrive.

So, you want to know the fate of the planet?

Figure out the fate of its bats.

“Bats are an index of environmental health,” said Jerry D. Hassinger, a wildlife biologist with the Pennsylvania Game Commission. “They’re sort of a barometer.”

For the last three years, Hassinger has been supervising a project that in June and July sent about 100 volunteers from across Pennsylvania out into the summer night, armed with pencils and survey sheets.

Their mission? Counting bats.

Granted, it might seem a bit batty for somebody in government to try to take what amounts to a census of creepy-looking flying mammals with no permanent addresses. Uncle Sam, it seems, has had enough trouble lately just counting people.

But Hassinger says there is some serious science behind the bat census, believed to be the first of its kind in the nation.

So serious, in fact, that the project is being funded for five years by the state’s Wildlife Resource Conservation Fund, a cooperative program of the game commission, the state Department of Environmental Resources and the Pennsylvania Fish Commission.

And last year, when the fund put out a call for volunteers to help with nearly a dozen wildlife-related projects, the bat survey surprised everyone by topping the list in the amount of public interest.

According to Hassinger, supervisor of the game commission’s unit for species of special concern, the bat survey is still a small-scale scientific endeavor.

And its value, he said, may not be known for 10 or 15 years, when the data surveyors are gathering now can be compared against newer data.

But what fund officials hope to do through the survey, he said, is to “take a snapshot” of how the state’s bats are doing now, especially in light of environmental pressures like diminishing habitat and human-introduced poisons.

In fact, Hassinger said, bats today are clearly under stress. They may look tough--and seem indestructible when you try to deroost them from your attic--but, he said, bats really are very sensitive creatures.

That’s because they’re insectivores, eating mostly moths, mosquitoes and other bugs.

“They, of course, are the things people spray,” Hassinger said.

When the insects get high concentrations of pesticides into their systems, he added, the poisons work their way up the food chain into bats.

Hassinger compares bats’ present situation to bald eagles’ a couple of decades back, when the eagles were being negatively affected by the pesticide DDT in their food supply.

“If we did in bats, we might want to ask why,” Hassinger said. “A dirty environment first affects these more sensitive creatures, and then it affects us.”

Ironically, if the number of bats were to decline, Hassinger said, that would mean insect pests would lose a natural predator, and still more spraying would have to be done to keep their numbers down.

“It’s a vicious circle,” Hassinger said.

Already, he said, at least some of Pennsylvania’s bats aren’t doing too well. In fact, of the five endangered mammals in Pennsylvania, Hassinger said, two are bats. One, the Indiana bat, is limited to one small wintering group in one cave in Blair County in the central part of the state.

“At last count there are roughly 300 of them, and we don’t know where they go in the summer,” Hassinger stated.

The other endangered bat is the Small-Footed Bat, which lives mostly in southwestern Pennsylvania. Interestingly, the 1988 and 1989 bat trend surveys found its small numbers actually increasing, Hassinger said. Alert surveyors were able to expand the number of known caves it lived in from one to 31, he said.

Hassinger said that is the kind of information the surveys are designed to root out.

Jim Schneck, a volunteer bat-watcher from Emmaus, has been ferreting out information about local bats ever since the project began.

A plant inspection specialist for AT&T; in Allentown, Schneck is an amateur cave explorer who got interested in bats as a sidelight of his hobby.

“The caving community is a strong supporter of bats, because you’re in their environment,” he said. “You’re seeing them up close and seeing where they live, and you see they ain’t such bad little guys.”

Two evenings last month, just before dusk, he said, he and his anthropologist girlfriend staked out their usual spot along Emmaus’ fitness trail near a pond to watch for bats.

As in previous years, Schneck said, they drew an imaginary line in the sky and counted the number of times bats crossed it. Such fly-bys, called “bat passes,” tend to be an indication of the food supply in a given area.

Bats are generally more active over water or around forests than in open areas, Hassinger said.

Besides the bat activity survey, which does not necessarily indicate the number of bats that live in a certain area, the bat census project includes a bat concentration survey.

“That’s counting the bats in the belfry, so to speak,” Hassinger said, noting the point is to “send people to where the bats live, and the largest number we’ve found so far are sleeping in church belfries.”

Game commission experts are also going into caves in the wintertime to count hibernating bats, he said, but no volunteers are being sent into caves because generally, “it’s considered too dangerous.”

According to Hassinger, last year, summertime bat activity observers tallied 11,691 bat passes for an average 104 per site. In 1988, observers tallied 8,239 bat passes for an average of 103 per site. The figures for 1990 are still coming in, he said.

Hassinger said conclusions from the data may be hard to come by because of variables in weather, insect population, times of surveying, habitat location and the abilities and inclinations of volunteers.

Still, Hassinger said, the 1988 and 1989 surveys have led to some interesting information.

One discovery, he said, is that large amounts of forest land, high temperatures and low winds correlate highly with high bat activity. So-called “cultural habitat”--buildings and suburban areas--were negatively associated with bat activity. Bat activity also was positively associated with wetland areas.

And last year, Montgomery County had the site with the highest number of bat passes--somewhat surprising, Hassinger said, because it is a densely developed county.

The amount of bat activity there, he said, might stem from a higher insect population or a large number of barns and other roosting places.

Or, he speculated, “Montgomery may only have a few places (for bat activity) left,” noting that might mean bats in that county have become concentrated in a sort of “bat ghetto.”

Hassinger said that one use of the data gathered by the surveys might be to single out sites that consistently record high numbers of bat passes as “best summer habitat.” Those sites could then be studied and possibly protected as a way of ultimately protecting bats.

“What we’re interested in as a special concerns species biologist is seeing that future generations inherit everything we inherited, and that includes species we don’t like--the snakes, the bats.”