On a sunny but cool morning, Heather Milligan bushwhacks through willows and steps over fallen trees along McIntyre Creek, in Whitehorse. The water babbles along on her left; across the creek, spruce trees rise towards the sky. Milligan, project biologist, and Kaz Kuba, program technician, are here to collect the ultrasonic detectors that have been positioned along the creek for the last two weeks.
They reach a willow bush with a long pole sticking out of it. A microphone affixed to the top points out over the creek. Milligan unwraps a black wire from around the bush and pulls out a small black box that contains the recording equipment. Both memory cards inside are full.
Milligan and Kuba will bring the equipment back to their office, where the data will get downloaded, then the detectors will be redeployed at another location. By the end of summer, the team will have audio files from more than 45 sites along McIntyre Creek.
Biologists can learn a lot from audio monitoring since bats use echolocation to navigate and find food, communicating at a higher frequency than humans can hear. (Bats are not blind, contrary to popular belief, but because they travel in darkness they rely on their ears much more than their eyes.)
Their echolocation sounds vary depending on what they are doing. When bats are merely flying from one point to another, their calls are more spaced out. But when they’re feeding and zoned in on a mosquito, for instance, their calls become much more frequent.
“They get what we call a feeding buzz,” says Jung.
By eavesdropping, biologists can learn how bats use different areas.
“I expect that there are a lot of flying insects around the creek,” says Milligan. “There’s an opening in the canopy as well,” she continues, gesturing to the sky, “so they can come down lower and feed. It might be a movement corridor, but it also might be a feeding corridor.”
It’s not easy studying these animals. Technology used to study larger mammals—like radio collars—hasn’t been miniaturized for bats.
“Instead of sitting at my desk looking at computer data on bison and where they went last Tuesday, the only way to get that information for bats is to actually be walking around, following them, monitoring them,” says Jung. “It’s a lot more hands-on.”
In addition to learning about bats, there’s value in learning from them. Bats are an indicator species, a gauge of the whole ecosystem’s health.
“They’re at the top of their food chain, just like grizzly bears are at the top of their food chain,” says Jung. “You can get a sense of how well an ecosystem is doing by studying those species that rely on the whole system working well.”
Despite their status on the food chain, bats are facing threats. Little brown bats have been decimated across North America by white-nose syndrome, which causes them to fly during daylight and wake too early from hibernation. They typically become weak and emaciated, making them easy prey for birds, like hawks. The disease hasn’t yet been found in Yukon bats, but it’s expected to make its way here. Because bats are slow to reproduce, it can take them years to recover from disease, habitat loss, or poor weather.
Then there’s also the conflict that inevitably comes from their desire to roost in warm, cozy places—most people don’t want bats as a roommate.
The department of environment tries mitigating this by teaching people how best to evict bats from homes and sheds and when, so as not to interrupt their nursing. Its website has instructions for building a bat house and a brochure offers some incentive: “You can give bats a place to live while benefiting from their insect control services.”