Bat species considered to be at risk seem to be in "relative abundance" on the east coast of Vancouver Island.
Scott Wilson, wildlife research biologist with Environment and Climate Change Canada, gave a first look into data he's been gathering during a presentation Thursday, Feb. 20, at the Beban Park Social Centre, hosted by Nanaimo and Area Land Trust and Nature Nanaimo.
"I've worked on migratory birds most of my life and the bats a bit more recent, and we know so much less about bats in comparison to migratory birds," said Wilson. "I'd say we're where we were 30 years ago with birds in terms of understanding their habitat needs and their ecology and so on."
Conducted from 2022-24, Wilson's research involved installing acoustic recording devices at 132 sites on the east coast of Vancouver Island from May 20 to July 10, designed to pick up the frequency of bat calls. The goal was to learn about the abundance of bat species, and the specific biomes each species prefers for feeding.
"The surveys showed a higher occurrence and relative abundance, especially for species at risk," Wilson said. "This is an area that still has a lot of little brown myotis, a lot of silver-haired bats, a lot of hoary bats … These are three species that are in trouble, and there is a lot of interest for [them] in Canada. Nanaimo is supporting good numbers of these species."
Wilson noted that some species call in similar frequencies, meaning that only some calls can be definitively identified to a species, while others can only be identified to a group of two or more species. For example, the California myotis and Yuma myotis call in the 45-50kHz frequency range, little brown myotis and long-legged myotis call in the 40kHz range and silver-haired, hoary and big brown bats call in the 25kHz range. Another aspect to keep in mind with the data is that the same bat will make multiple passes by the acoustic recorder while feeding. Therefore, the number of calls is not a measure of the true number of bats at a site, but as long as the survey methods are consistent, the number of calls can be used to indicate the relative abundance of different species or species groups and thus their preference for feeding in different types of habitats.
The data shows that in the Nanaimo area, wetlands were significantly preferred by the myotis species, with a relative abundance 6-10 times higher compared to non-wetlands. The wetlands were also preferred by the silver-haired hoary and big brown group, but less significantly, with the species also frequenting meadow bluffs.
"Wetlands are productive feeding sites, high insect abundance and that's drawing in those species that feed out in open areas, aerial hawking species they'd be called, as opposed to species like long-eared myotis that are more of a gleaning species."
A preference was also shown in the data for the proportion of forest cover around two kilometres from the site, with bats preferring intermediate levels of cover to different extents.
When it's low forest cover, around 20-40 per cent, bat activity is also low. Activity increases up to around 65 per cent, most notably in the little brown myotis and long-legged myotis species. The silver-haired, hoary and big brown grouping prefer sites around 50 per cent forest cover within two kilometres. The long-eared myotis, however, didn't appear to share this preference, and preferred greater forest cover during the survey.
At Morrell Nature Sanctuary, recordings picked up 1,302 calls a night with species including the big brown, hoary, silver-haired, little brown myotis, California myotis, Yuma myotis and long-legged myotis. The only species present on Vancouver Island not identified at the site were the uncommon Townsend's big-eared bat and long-eared myotis. Buttertubs Marsh had just 209 calls a night on average, with the hoary, silver-haired, little brown, California and Yuma.
"Morrell is an example of a site that still has a lot of forest cover around the site, I think it's about 65-70 per cent," Wilson explained. "Buttertubs, excellent marsh, but a lot of urban area around it. It's only about 20-25 per cent."
Some other sites included Yellow Point Bog, which had 1,108 calls per night on average; Linley Valley, which had an average of 515 calls; Richards Marsh with 393 calls and Mount Benson, which had 378 calls.
"The main home takeaway here is wetlands are super important, especially for myotis," Wilson said.
A draft of his full report is planned to be completed next month, to be published in scientific journals later this year.
To support bat conservation, Wilson said there are several things that average person can do to help bats in their community including participating in monitoring initiatives, helping protect wetlands, keeping domestic cats from roaming, and maintaining bat-friendly yards with vegetation and no pesticides.
People can learn more about getting involved in local bat conservation through the B.C. Community Bat program at http://bcbats.ca/get-involved.
