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 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 or territory: in Quebec: Info-Santé – 8-1-1, in Ontario: TeleHealth – 1-866-797-0000, in Manitoba: Health links – 1-888-315-9257, in Saskatchewan: Health Links – 8-1-1, in Alberta: Health Links – 8-1-1 (or 1-866-408-5465), in the Yukon: HealthLine – 8-1-1.
Although it is more common for bats to enter houses in the summer, the big brown bat sometimes enters houses in the winter. This behaviour is commonly associated with periodic arousal from hibernation. Because bats are sensitive to temperature changes, individuals may sometimes wake up and enter a house during winter thaws or bouts of extreme cold. When this occurs, bats are frequently be found near sources of water (e.g. toilet, shower, sink) because they need water between bouts of hibernation.
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.
Signs indicating the presence of bats in a house
- Various noises such as scratching or squeaking.
- Bat guano is segmented, elongated and brittle
- It becomes powdery when crushed
- It gives off an unpleasant smell when the maternity colony is large
- Guano often becomes stuck to walls, where the bats enter their colony
- Attention - Bat feces can cause histoplasmosis, which is a pulmonary infection that results from a fungus found in guano. Generally, this fungus does not survive in hot and dry attics; however, in order to avoid any risk of contamination, it is recommended that you carefully follow certain preventative measures
- It crystalizes at room temperature
- It makes the area where it has been dropped seem powdery
Tips for cohabitation
- Bats do not cause the same level of damage as the rodents that can live in our houses. Bats only enter through pre-existing holes and often occupy non-utilized areas, like roof spaces. The main nuisance associated with bats is their guano. To avoid the problems associated with guano, you can place a plastic tarp on the area below where they are roosting early on in the spring. This way, you will be able to clean up after them more easily at the end of summer when the bats have left to spend winter in a hibernaculum.
- There is no reason to panic if you think there are bats living in your house because the probability of one of them having rabies is very low. Like most mammals, bats can contract the rabies virus, but only 1% of them are infected. However, to be careful, you should avoid contact with bats in order to prevent becoming infected with rabies, which is lethal to all mammals, including humans. It is important to realize that bats found on the ground have a greater chance of having rabies. Therefore, it is important to never touch a bat bare-handed, even if it is dead click for more info.
- If a colony of bats has settled in your attic, it is important to caulk all holes and cracks between the attic and the lived-in areas of your house.
- If a bat enters the living-space of your house, never touch it bare-handed. Close the door to the room and open the windows and screens. It should leave by itself. If this does not work, follow the following guidelines. Next, find the hole where it likely entered the house and caulk it.
- Do not go into areas inhabited by bats while they are there. In order to see them, wait for them outside and watch for them to leave after the sun has set. To confirm that you have a maternity colony, follow this protocol. If you perform a count of the number of bats in the colony, you can submit the data to us here
- Make sure that your pets are vaccinated against rabies. This is a basic but very important rule, especially if there are bats are living in your home. Rabid bats are often found on the ground, which makes it more likely that your pets will come into contact with them. Pets also require booster vaccines for rabies. Consult your veterinarian for further information.
- Another way to live with bats on your property is to set up bat houses on your property. If bat houses are installed near the building where the bats lived, the colony will often move to the bat house. For more details, see "Setting up a bat house"