Ask a biologist what's the least understood of all the mammals. Chances are the answer will be bats. There are around 1100 species of this nighttime flyer worldwide. They're found almost everywhere except for the most extreme desert and polar regions. The United States is home to 47 species. High-tech gizmos are shining more light on the secret life of bats. Tom Banse takes us on a nighttime fieldtrip.
What sounds like crickets on this late autumn evening is actually the sound of one of the rarest of the Western U.S. bats, the spotted bat as it hunts for moths to eat. It has huge pink ears and a wingspan of a third of a meter. Its feeding call was recorded by a biologist in north-central Washington State, in an arid gorge known as Moses Coulee. The remote location is a hotspot for bats, and a good place to investigate basic questions that we still don't know the answers to in 2007. Like, how many bats do we have? Where do they go for the winter? Are they doing well or poorly? Why are they important to us?
The answer, according to The Nature Conservancy's Chuck Warner, is because we don't know how important they are to us. "We don't want to jeopardize something or lose it before we find out what kind of value it can hold, not only economically, but intrinsically, biologically," he explains.
Bats probably consume large quantities of pest insects. We can't observe that first-hand because they fly around in the dark and mostly make sounds we can't hear. "They're a hard animal to study," Warner admits. "But the technology is just now coming to a point where there's going to be a huge turnabout in the amount of information and data that we can gather."
The technology starts with the bat detector, a handheld recorder that can shift the frequency of bat calls into the audible range. At the field station, wildlife biologist Katy Warner (no relation to Chuck) uploads recordings into a specialized software program called Sonobat. It slows the bat calls down for analysis. "It's pretty hard to do the identification in the field," Warner points out. "You pretty much need to bring the calls back and look at them with the Sonobat software." When the calls are replayed ten times slower than in real life, it's easy to hear the difference between the spotted bat and the western pipistrelle, for example.
Efforts are underway to enhance the software to create an automated voice recognition system for bats. That would make it easier for land managers to identify which species are present and possibly in need of protection. Meanwhile, scientists in Texas are experimenting with infrared thermal imaging to count and identify bats in the dark. Miniaturized radio tracking transmitters are also under development.
Still, there's a place for old-fashioned fieldwork. On a moonless autumn night, 20 Nature Conservancy volunteers and staff are strung out in a long line down Moses Coulee. Margaret Amara is counting spotted bat calls while her husband logs the activity patterns by flashlight. "I was worried that you would have to look at them and they would come flying at you," she admits, a bit sheepishly. "They said, 'No it's all by sound.' I go, 'I can do that.' Yeah, I wasn't real fond of bats, but now I have a new thinking about bats. They're pretty amazing, what they do."
One area of emerging concern: the burgeoning number of wind farms in North America. For unknown reasons, some bats fail to recognize the threat posed by the whirling blades. They fly into them and die. Over the past two summers, a study outside Lakeview, Oregon, investigated whether high frequency loudspeaker broadcasts could deter bats. The next stage in the study is to test the devices at an actual wind farm.