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Science and the Environment

Mysterious NWS Radar Signature Turns Out to be Bats

U.S. Fish & Wildlife Service

A unique relationship has developed between the National Weather Service and the Missouri Department of Conservation.  And it all started with something forecasters spotted on radar.  KSMU’s Michele Skalicky explains.

Last year, forecasters at the National Weather Service Office in Springfield were monitoring radar when they noticed something out of the ordinary.  Meteorologist Drew Albert says there were radar signatures in June in the evening hours—right after sunset—over Dallas County, and they continued over the course of the summer.

They re-emerged this spring, he says, and forecasters are still seeing them when radar conditions are good.

Albert says they had an idea of what the radar signatures could be, but they weren’t 100 percent sure.

"We made some assumptions initially.  We do know that National Weather Service radar can pick up what we call biological scatterers, and that can include birds, insects and of course bats, and it was assumed they were bats just because of the time of day," he said.

According to Albert, out west in places like southern Texas, Mexican free-tail bats show up easily on radar because of their large numbers and how high they fly.  But in Missouri, bats tend to fly lower when foraging, and their numbers are smaller.  Albert has a theory.

"During the evening, the beam does get bent downward a little bit towards the ground as what meteorologists call a night time temperature emergence sets up, and that inversion sets up, and that inversion sets up as the ground cools, so the beam does get bent downward just a little bit, and also the beam will spread out with distance from the radar, too," he said.

The echoes they were looking at, he says, were 20 to 30 miles from the radar.  Forecasters posted what they were seeing on social media, hoping to get some answers.  The findings eventually got to the Missouri Department of Conservation, which determined that the radar signatures were endangered gray bats emerging at night to eat insects.  And this particular colony—whose location is being kept under wraps to protect it—was unknown to MDC biologists.

Tony Elliott is the Conservation Department’s bat biologist.  He says they’ve been tracking gray bats closely, and he's excited about the findings by the National Weather Service.

"This is an encouraging sign in the fact that there are significant colonies around--at least one--that we didn't know was there," he said.

According to Elliott, there are just three main hibernation caves for gray bats in Missouri, but in the summer they disperse to a larger number of what are called maternity and bachelor caves.  He estimates there are about 700,000 gray bats in Missouri.  But they face challenges—the number one being white nose syndrome, which has killed more than five million bats in the United States.  There have been both confirmed and suspected cases of the fungus in bats in Missouri.  The Conservation Department is trying to curb its spread by closing off caves to humans when bats are present. 

Another challenge for bats is disturbance by humans. 

"They are very susceptible to disturbance in the summer because they roost in subterranean habitats in large colonies, and, if they get disturbed, the young can be knocked to the ground before they can fly," he said.

And in the winter, bats can starve to death if awoken too often while hibernating.

Now that the Dallas County summer bat colony has been discovered thanks to radar, the landowner is working with the Conservation Department to protect the endangered mammals.  And the Conservation Department is sharing any new information it obtains about the bats with the U.S. Fish and Wildlife Service. 

Meanwhile, Albert continues to monitor the colony on radar, and he’s interested in using radar to monitor other species, too.  He says, what’s known as radar aeroecology—using radar to study things like migration patterns--is an emerging field, which he’d like to learn more about.  He’s a master naturalist, and he says combining his two loves—weather and nature—appeals to him. 

"My loose plan is to maybe more systematically follow these signatures with time to see maybe how the populations are shifting around, how things are changing with time," he said.

Elliott says they’re just beginning to study the bat roosting sites that were recently discovered.  He says he’s excited about the potential for using radar to monitor that colony and other wildlife.