FROM: Crowsnest Conservation WildEd
“Eye of newt, and toe of frog,
Wool of bat, and tongue of dog”
Stories, myths, and ancient legends, including this witches’ brew recipe from Shakespeare’s Macbeth, have long characterized bats as evil creatures of the night. But bats hardly deserve this reputation – many ecosystems would suffer greatly without the pest control and pollination services they provide.
Of the four species resident in southwestern Alberta, big brown bats and little brown bats are those most commonly encountered by people, and those to whom we owe the greatest debt. Many of the insect species eaten by bats are considered forest or agricultural pests or are a nuisance to people (such as biting insects). Little brown bats can eat up to half their own body weight in insects each night! A typical colony of little brown bats can consume up to 50 kilograms (110 pounds) of insects during the summer.
But is the writing on the wall for these winged wonders of the night? The three migratory species present in Alberta between early May and mid-September are provincially Sensitive due to potential impacts of wind developments during the fall migration period, and the little brown bat is federally Endangered under the Species At Risk Act due to the impacts of White-Nosed Syndrome.
White-Nosed Syndrome (WNS) is a fungal disease that damages tissues and causes bats to wake frequently during winter hibernation, burning through precious fat reserves. The disease has decimated bat populations in the eastern United States and Canada killing more than six million bats and is slowly spreading westward. Unfortunately, WNS appears to have leap-frogged west with the discovery of infected bat carcasses near Seattle last year.
Wildlife managers and biologists are now scrambling to identify locations of summer maternity colonies (where females raise their young pups) as well as important winter hibernacula for Alberta bats to protect them from the threat of WNS. But contrary to eastern roosts with thousands of bats, western bats seem to congregate in much smaller numbers and thus likely many more dispersed locations. Yet these sites are largely unidentified; in Alberta, three cave hibernacula discovered in the past two winters have housed only around 300 bats.
Although most of us probably wouldn’t have opportunity to encounter bats in caves, summer roosting and maternity colony sites are typically warm locations that promote growth of the young including buildings (e.g., attics, rafters, old barns, under siding), bridges, tree crevices or under bark, rock crevices, and of course bat houses.
Conflicts occur most often when roosts are found in occupied buildings. Bats do not gnaw like rodents, so they won’t gnaw their way into a building or chew wiring and insulation, but the volumes of urine and feces deposited as well as the incessant squeak of young while mothers are away are sometimes enough to drive people “batty”. Many are also uncomfortable with bat presence as they can carry rabies. Incidence of rabies is very low, but any bat displaying unusual, daytime behaviour should be reported to wildlife officials and anyone experiencing a bat bite should receive immediate medical attention.
If you must exclude bats from a site, consider installing a bat house nearby before evicting them to offer an alternative place to live and only exclude bats once they have left for the winter. Got Bats? Alberta Guide for Managing Bats in Buildings is available online and provides lots of great advice on properly managing bat issues including cleanup of bat guano and humane exclusion.
Perhaps most importantly, contribute to the conservation of these winged wonders by reporting any roosts you encounter to the Alberta Community Bat Program (email@example.com).