Silver-haired bats are literally singing for their lives. The discovery that silver-haired bats sing is allowing bat biologists to identify the species and record their locations, to help prevent them from being killed by wind-power development, says Cori Lausen, director of bat conservation with the Wildlife Conservation Society Canada in Kaslo.
“To be able to conclusively say we have silver-hair bats detected in this landscape will help us be able to say we probably shouldn’t be putting our wind turbines here,” said Lausen.
Silver-hair bats are a migratory species, except in B.C., where not all silver-haired bats migrate. The species hibernates in mines and trees in the West Kootenay and along the coast of Vancouver Island, said Lausen.
Quite a few European and some tropical bat species are known to sing as a mating ritual, said the bat biologist, an adjunct professor at Thompson Rivers University in Kamloops.
“A lot of the time, they will sit in one spot and sing … ‘Hey, I’m here and this is my territory. Females, come on, let’s mate. You’re welcome in my territory,’ ” said Lausen.
But researchers believe the silver-haired bats are not just sitting in a tree singing, but singing while they fly.
Bat biologist Tim Ennis, co-ordinator of the North Island chapter of the B.C. Community Bat Program and executive director of the Comox Valley Land Trust, recorded bats using a bat detector on the roof of his car as he drove through the Cowichan Valley.
He recorded several back-to-back songs, confirming that the bats were flying when they were singing.
“The night sky is a very lonely place to fly at night and they might feel like they are the only bat out there flying around for an hour,” said Lausen. “Then they go back in and they’re hibernating for another few weeks before they come out for another hour or two. That might be when they’re sending out the songs — ‘If anybody else is out here right now who wants to mate, I’m awake. And I have nothing better to do.’ ”
Their songs have helped biologists distinguish silver-haired bats from echolocation sounds made by big brown bats and hoary bats.
Silver-haired singing sounds like a little musical flute, a song that is repeated over and over again, said Lausen. It’s a set phrase with variations.
“The sounds are very quick. They happen really quickly, one after the other, which is really different from the way they echolocate,” she said.
With silver-haired echolocation, they send the sound out, then listen to the echo coming back.
“They have to have a lot of listening time between their calls,” she said. “The notes of their songs are extremely close together. There is no time for them to listen for echoes in between — that is why we’re convinced this is not echolocation.
“The songs are being produced for a very different reason. The repeated pattern goes from lower frequency to higher frequency.”
Migratory silver-haired bats and hoary bats have experienced heavy mortality from wind-power development and have been assessed as endangered by the Committee on the Status of Endangered Wildlife in Canada.
Being able to accurately determine which species are present in the area of existing or potential wind-power developments can help with mitigation and monitoring.
If wind turbines are put in the path of migratory bats, it’s pretty much guaranteed that they will slowly kill off these species over time, said Lausen.
“We can reduce the kill rate, but we can’t completely stop operating turbines from killing bats, so it’s really important that those turbines don’t get put in the wrong location,” she said.
“This will be one more tool in the toolbox if we can concretely say silver-haired bats are in this area or are migrating through this area.”
The forestry industry should also be aware that silver-haired bats are hibernating in trees in the milder climate of southern B.C. A lot of logging happens in the winter in B.C. to protect songbirds nesting in trees.
For years, Lausen has made recordings of the songs outside two old mine sites in the West Kootenay, and was able to conclude the songs were produced by silver-haired bats after capturing them in mist nets from 2015 to 2018.
She was also the first bat biologist to document the fact that silver-haired bats mate in winter.
“And the fact that a lot of songs are produced in winter is further evidence these songs may be tied to mating,” said Lausen.
The Brazilian free-tailed bat, also a singing bat, was discovered on Salt Spring Island by Vancouver Island biologist Peter Ommundsen.
Lausen has recorded that species singing on Salt Spring and Texada islands, the Port of Vancouver and the Cowichan Valley.
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