In lightless arks of life

Bats: Deep in Maryland's dank limestone caves, scientists tally the state's 17 species of the poorly understood mammal.

February 21, 1999|By Heather Dewar | Heather Dewar,SUN STAFF

GRANTSVILLE -- Imagine a world with stone skies smooth as silk, pleated and whorled like the folds of a collapsing circus tent, soaring up into darkness, sagging within inches of the ground. Imagine chill, dank air with no hint of a breeze and darkness so absolute that no sun-loving plant, not even single-celled algae, can survive.

There are 161 such worlds in Maryland, and scientist-spelunker Daniel Feller has explored most of them. He knows what the rest of us can barely imagine: that the state's limestone caves are lightless arks full of bizarre, stubborn life.

There are snails smaller than a pinhead, living for years in inch-deep pools of water.

There are blind albino crustaceans, carrying their young clutched to their chests to save them from being cannibalized. A colony has lived for years on the dribble of nutrients from the skeleton of one dead mouse.

There are beetles with sniffers so refined that they travel thousands of yards through a cave on the trail of the tiniest smidgen of food.

Alone, none of these creatures could survive in the nourishment-starved caves. Their lifelines, bringing seeds and insects and nutrient-packed guano from the sunlit world, are an unlikely trio of saviors: bats, rats and salamanders.

Feller is an expert on all three. A biologist for the state Department of Natural Resources, he has waded in icy streams, turning over rocks to find rare hellbender salamanders. He has inventoried the contents of pack rats' nests: shotgun shells, scraps of tinfoil, stolen eyeglasses and other shiny things. But his true passion is cataloging the creatures of Maryland's caves, especially bats.

Feller is cheerfully obsessed, the kind of guy who encourages little brown bats to nest behind the shutters of his house and remembers the exact date he saw a rare red bat flying nearby ("It was Dec. 6, 1996"). It is his job to keep tabs on Maryland's 17 species of bats, which are poorly understood but believed to be barely holding their own against the pressures of development.

Once every two years, Feller's work takes him a third of a mile underground in Garrett County to tally bats in the caves where they sleep away the winter. This year he is accompanied by Frostburg State University biology professor Richard L. Raesly, an equally sunny sort whose favorite User.Event 7 was not expected here! phrase is "No worries," and graduate student Salvatore Agosta, an expert on the rain forest bats of Ecuador.

All three men think these maligned mammals deserve more respect for the services they provide humans. Bats come in nearly 1,000 varieties, each equipped with night-flying sonar so sophisticated that high-priced military research can't match its precision.

In the tropics, fruit-eating bats pollinate bananas and mangoes, cashews, dates and figs. In temperate places such as Maryland, a single insect-eating bat can catch 1,200 mosqui toes an hour, according to Bat Conservation International. A colony of 150 bats can gobble up 33 million root worms before the worms gobble up precious crops. And yes, they carry rabies, says Raesly, but far less often than raccoons.

Some species threatened

Still, bats and humans don't mingle well, and at least two local species are in trouble.

The Indiana bat, which summers in the hollowed-out hearts of dying trees, is losing its habitat to logging, and is on the federal list of endangered species.

And the little brown bat is classified as "in need of conservation" in Maryland. In the wild, the small, sable-colored creatures raise their young under loose tree bark. When houses are nearby, they often roost in attics or behind shingles.

"That usually works fine until people get scared and start killing them," Feller said.

Widespread pesticide spraying for gypsy moths has probably hurt bat populations by depriving them of insects, says Feller, though the data are scarce. Mining damages their winter shelter, subtly altering the precise balance of temperature and humidity needed to send the creatures' heart rates tumbling from flight speed of 1,000 beats a minute to resting rates of six beats a minute or less.

Even spelunkers are a threat. In the fall, bats gorge themselves on insects to pack on a layer of fat for hibernation. The bats' surplus is small, and when cave explorers' footsteps and bright lights disturb them, they can burn up so much energy that they die of starvation before winter's end. That's why Feller limits his tally to two caves in Garrett County. Both are owned by the Nature Conservancy and barred by heavy steel gates, and he won't publicly name them.

A 15-foot drop

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