With Halloween only days away, bat images and decorations abound. In books and film, bats are depicted as the consorts of witches and are associated with black magic; they are the shape-shifters, vampires who live for all eternity.
Bowen’s bats are not vampires and as far as an ability to live forever, our little brown bat can live an impressive three decades. They eat mosquitoes that suck blood, but they themselves, do not.
Insects that fly at dusk are the choice of food for local bats that may be active at dusk and dawn, at night or both periods. They hang upside down to sleep, but some will hibernate furled in crevices in rocks, or between stacked logs. They can see quite well, but tuning into echoes of their own ultrasonic voices, they can echolocate objects as fine as a human hair and can therefore fly with amazing accuracy. Though small with big ears, an attribute that has given some species their designation as the group with “mouse ears,” or “Myotis” bats, they are not rodents. They are the only mammals that fly and are not related to birds.
Of the 16 bat species found in the province, the Bowen Island Conservancy recently discovered six species at their new conservation area; this includes a federally designated endangered species, the little brown myotis.
Jeff Matheson, a volunteer biologist for the conservancy initiated the research on the site with a loan of audio recording equipment that identifies ultrasonic bats chirps as they echolocate insects. The equipment on loan from Tetra Tech Canada captured vocalizations specific to six bat species, and possibly more.
Matheson is part of a team of biologists, including Will Husby and Alan Whitehead, volunteering their expertise to the Conservancy as the organization works feverishly to learn about species at the site as they plan for the gradual opening of trails. “You’ll only get one chance to get it right,” cautions Matheson, in reference to human impact on animals and plants. Preliminary research like this study is key.
The team selected monitoring stations with potential food sources and possible roosting sites. Though bats can be heard chirping to communicate with each other, the equipment recorded and analyzed the otherwise inaudible-to-human echolocation bats use to zero in on food sources: termites, carpenter ants, wasps, beetles, moths, mosquitoes. The large bats vocalize with lower frequency echolocation than smaller species. The lower frequency detects larger prey, such as hard-shelled beetles, carpenter ants and termites. Smaller bats emit higher frequency chirps that target small, soft-bodied insects.
Matheson analyzed the recorded data and was surprised at the results. “There were definitely more species than I expected.”
Without capturing bats, or analyzing their droppings, biologists can’t claim 100 per cent certainty on the identification, but between the men and machine, there is a “high level of confidence” that the area hosts at least six types of bats. We may also have two others: Townsend’s big-eared bat and big brown are likely to be present, but not recorded. This would bring bat species to eight, representing half of all the species in the province and a large percentage of all bat biodiversity in Canada.
According to the study, the conservation area hosts Canada’s biggest bat, the hoary bat, and one of the smallest, the aforementioned little brown myotis. “Myotis” the “mouse-eared” bat species include the Californian, western long-eared, yuma, and long-legged myotis, all of which were discovered by the Conservancy last summer.
The hoary bat, considered to be migratory, is 13 to 15 cm long with a wingspan of 36 to 41 cm; they are strong fliers who may migrate as far as Mexico. The silver-haired bat, another species documented, may migrate south where they may remain active or hibernate, or they may remain on island. Unfortunately, information on B.C. bats is sketchy,
On Bowen, the Californian myotis, western long-eared myotis, yuma myotis and little brown myotis are species that are likely to stick around over the winter. Some types will use bat houses, others have specific needs more suited to rotting trees, or caves. The little brown myotis weighs as much as four pennies but may travel hundreds of kilometres to a hibernation site, returning there year after year. They will also use bat houses.
Matheson says, “Bats are not well-studied compared to other animals. Because they are nocturnal and not easily observed, there are poor records in our region.” In addition, “there are concerns about decline due to changing prey availability, and white nose [syndrome].” The biologist also wonders what effect the extreme heat had on insects that are prey for bats. “It’s something I’d be interested in finding out.”
Unfortunately, half of B.C. bat species are vulnerable, threatened or endangered. Some of the bats migrate and some hibernate. White nose syndrome and Pd, the fungus responsible for devastating bat populations east of B.C. is beginning to be a threat too in this province, having been recorded as close to Bowen as Seattle. While no threat to humans, it’s putting some bats, like the little brown on the brink of extinction in some places.
The species most affected are those that hibernate in colonies.
Roosting is when bats shelter for sleep, but are active, not in hibernation.
It’s common for bat moms to form maternal colonies where they collectively raise the ambient temperature around their babies. It also makes an entire bat nursery vulnerable to a single threat like the felling of the tree where they are gathered.
Depending on the species, bats roost or hibernate in buildings, behind bark in dead trees, tucked deep into crevices in rocks, or in your woodpile. Disturbing a hibernating bat is very hard on the bat as it forces it to use its body’s fat stores as it seek out a new site. If you find one outside, the best thing to do is leave it under cover, undisturbed.
“The research sets a baseline for future monitoring,” says Matheson, adding, “further analysis may tell us about habitat association and use.” For now, this first research project reinforces the value of conservation areas as places for biodiversity and the joys of nature exploration and discovery.
