October 30, 2007

Researchers Study Bat Colony in Wash.


The large clearwell near the Columbia River was once used to hold filtered water for Hanford's F Reactor when it produced plutonium for the nation's nuclear weapons program. Sometime after it stopped operating about 30 years ago, one of its six hatches was left open, providing a doorway for the bat colony.

Researchers have twice tried to count the bats by setting up a video cameras with an infrared light outside the hatch. Both times they've counted about 2,000 bats, which they consider a low estimate. The number still makes the colony among the largest identified in the state.

However, the clearwell is scheduled to be demolished in fiscal year 2009, which begins next October.

"That (gives) us some time to figure out how to deal with it," said Ken Gano, a natural resource specialist for contractor Washington Closure Hanford. "We can look at the impact to demolishing it and what we can do to provide an alternate roost site."

Although they are small animals, it's a big issue for the Department of Energy, whose policy is to manage the Hanford cleanup with as little impact to plants and animals as possible. Under a presidential order, Hanford must protect animals and other natural resources to allow more of the site to possibly be added to the Hanford Reach National Monument.

The bat colony qualifies as a priority species designation for the state because it's a maternity colony, with females spending the spring and summer roosting in the clearwell while each raises a single pup. It's so large that there is a possibility it's populating the entire region.

Researchers believe the bats are a type called Yuma myotis. They have furry brown bodies with black wings. Each Yuma myotis weighs about 6 to 8 grams - less than two nickels - and has a body smaller than a mouse. But they look bigger in flight because of a wing span that stretches 6 to 8 inches.

Hanford researchers went inside the clearwell a couple of weeks ago. They found about 30 bats still in the clearwell at the end of summer, but plenty of evidence that more had been there.

The bats migrate to hibernate when the weather gets too cool for them to find the insects they need.

The researchers found still more bats when they entered a 700-foot-long flume adjacent to the clearwell that was used to carry water in and out.

During the next year, researchers hope to learn more about the genetic relationships and diversity within the colony, providing information about the colony's regional importance. The research also should answer what temperature and humidity the Yuma myotis requires for roosting with data from sensors placed inside the clearwell and flume.

"There's not a lot of information about bats and what their habitat requirements are," said Jon Lucas, an environmental specialist for Areva who is working on the research as part of his work to earn a master's degree.

Acoustic sensors will provide information on when the bats show up next spring and also information about when they come and go daily.

In about a year, the Energy Department should be ready to make a decision on what to do with the colony.

