Because bats are nocturnal, they must find shelter during the day where they are not vulnerable to predators. If bats are able to find a suitable site, they will return to it year after year. Depending on the season, these sites may be abandoned mines, caves, trees, bat houses or even our houses.
Why do bats roost in our houses?
There are many reasons why bats choose our houses as roosting sites during the summer. The first is that the conditions in our houses are favourable for bats to raise their young. Female bats typically seek out warmer temperatures. Pregnant females and females raising pups often like to roost in attics or walls, where heat accumulates. The higher temperatures in these areas is advantageous during pregnancy and increases milk production. When many reproductive females live together, this is called a maternity colony. Maternity colonies are typically occupied between June and August.
It is important to not disturb maternity colonies, because some of the young may not know how to fly and could die from being trapped or left behind. If maternity colonies are disturbed, this could lead to unpleasant smells in your house, or bats coming into the living spaces. If you absolutely must remove a maternity colony, please follow the instructions provided here. To learn how to live with harmoniously with bats in your house, refer to the following section: Live in harmony with a colony of bats.
It is also possible to find solitary bats roosting in unprotected chimneys and air vents. These areas are generally used for shorter time periods. Bats usually do not enter houses, but they sometimes get lost and enter them by accident. Bats that accidentally enter houses are often young and relatively inexperienced fliers.
Be careful! Bats are easy to observe, however we strongly suggest that you do not touch them because they may carry rabies. If you come into physical contact with a bat, call the number associated with your province: in Quebec: Info-Santé - 8-1-1, in Ontario: TeleHealth - 1-866-797-0000, in Manitoba: Health links - 1-888-315-9257.
Although it is more common for bats to enter houses in the summer, the big brown bat (Myotis fuscus) sometimes enters houses in the winter. This behaviour is commonly associated with juveniles who, unlike adults, did not migrate to hibernating sites (e.g. caves, abandoned mines) during the fall. Because bats are sensitive to temperature changes, individuals may sometimes wake up and enter a house during winter thaws or bouts of extreme cold. Juveniles generally have smaller fat reserves and can be forced to search for food and water to survive the winter. When this occurs, bats are frequently be found near sources of water (e.g. toilet, shower, sink) because they need water between periods of inactivity.
IMPORTANT: If you find a bat in your house, please follow these instructions
Why is it beneficial to protect our bats?
Bats play an important role in ecosystems. All of the bats in Canada are insectivores. As a result, they are important predators of biting insects, and pest species in the forestry and agricultural sectors. By consuming these insects, the use of pesticides can be reduced, which benefits the quality of soil and water.