Thursday, Jul. 24, 2008

Search for rare big-eared mammal yields bonanza in midstate

Black leaves squelching underfoot released a musty aroma of decay as Matthew Clement picked his way through a miniature forest of cypress knees in the Beaverdam Wildlife Management Area. When he reached a giant water tupelo, he twisted his body and smoothly disappeared inside.

He shone a high-powered flashlight up. Twenty feet above clung a rare animal: the tiny Rafinesque's big-eared bat. Clement's graduate research about these little-understood bats has revealed a significant population of the animals in Middle Georgia's bottomland swamps.

Beaverdam WMA, in Laurens and Wilkinson counties, has a healthy population. The Ocmulgee WMA, located in Twiggs, Bleckley and Pulaski counties, was the second-best site for big-eared bats among the eight areas Clement studied during the past year.

Before Clement began his work, which is funded through the Georgia Department of Natural Resources, only 17 big-eared bats had been found in all of south Georgia. Jim Ozier, program manager for the DNR nongame section, said they were believed to live only near the coast. Another subspecies lives in caves in north Georgia.

As he studied a broader area below the Fall Line, Clement's goal was to find 30 bats, he said.

So far, he has found close to 900.

The creatures weigh less than a third of an ounce. Like other bats, they use high-frequency, loud calls to navigate in the dark, a method called "echolocation." The way their calls echo back reveals information about what's in front of them.

Scientists speculate about the reason for the size of the Rafinesque bat's ears, which are sometimes compared to a rabbit's.

"It's thought that the big-eared bat can hear so well that it can hear the sound of a moth walking on a leaf without having to echolocate," Clement said.

Ozier offers another possible explanation for why this species evolved big ears. He said the bats are slow flyers as they navigate through the woods. This might mean it's less important for them to be aerodynamic than for them to be able to process more information about oncoming obstacles.

Bats are valuable to the ecosystem because they eat night-flying insects and valuable to humans because some of those insects are mosquitoes and the moth forms of major crop pests, Ozier said.

Although many bat species gather in colonies ranging from hundreds to tens of thousands, the Rafinesque's big-eared bat can often be found alone or in groups of several dozen, Ozier said.

HAND MIRROR HELPS

Tuesday, Clement walked transections in the Beaverdam WMA swamp that had been chest-deep in water this spring. He checked hollow trees for daytime-sleeping bats. He has found 28 roost trees at Beaverdam WMA so far.

Some of the tree openings were so small or strangely shaped that Clement had to angle a hand mirror to search for the bats. Other hollow trees can't be checked because the opening is too far above the ground.

Many bats seem to switch roost trees each day, he said. The males rarely move more than 10 or 20 yards, but some females Clement was radio-tracking have disappeared. Clement speculated that the females probably have to go farther afield to meet specific roosting requirements for their babies, called pups.

The swamp is surrounded by 2-inch sweet gum trees that grew after past timber cuts. But loggers left behind the old water tupelo, because even the healthy ones consist of a 3-inch wood shell surrounding a 3-foot-wide hollow space.

Big-eared bats are the beneficiaries.

Clement has found more of the subspecies than he expected, but his research also revealed they need this very specific real estate. Not caves. Not barns or houses. Not even upland pine forests.

Previously, scientists thought big-eared bats lived in a variety of habitats, Clement said. But he focused his research on areas in the National Wetlands Inventory, guessing that the big hollow trees would be the key.

"I bet my project that's where the bats would be," he said. "And that's absolutely where the bats are. ... I've come out here at night with a flashlight, and there are bats everywhere."

They seem to prefer trees that are the most smooth and clean inside, he said.

"If you as a person were condemned to live in the swamp, you'd pick the same tree the bats do," he said.

However, you might have to share the space with swarms of mosquitoes and spiders far larger than the bats.

Clement started out last summer netting flying bats and radio-tagging them at night, checking trees by day and putting out ultrasonic microphones to track bats. But he found so many that he was able to abandon some of the less-productive methods.

Clement gathers extensive information about what kinds of trees the bats prefer. He measures the height and diameter of each of the 170 roost trees he has found, as well as many of the 1,400 or so other hollow trees he has come across.

He also notes whether each tree is in standing water, the size and nature of the interior space, the size of openings in the tree and their distance from the ground, and the number and size of surrounding trees.

Electronic monitors track temperature and humidity inside some of the trees.

At the end of the summer, Clement will examine all this data to find patterns that might reveal more about what conditions the bats need.

Ozier said the bats could be a good indicator species for the health of Georgia's bottomland forests.

"Drought and changes in wetland regulations have opened up a lot of these areas for logging in the last couple of decades," he noted. "Matt's research could help us look at current and future bat management and help us pinpoint areas where these bats are likely to live so we could work out agreements with landowners."

To contact writer S. Heather Duncan, call 744-4225.