Even though Big Brown Bats may cause some problems in urban areas, it is mainly their smaller cousin that infests our buildings. These small flying mammals play a key role in insect control. One colony of 500 bats eats one million insects each night! Bats help keep ecosystems in balance. Not only must they be protected because of their important ecological role, but also because their populations are declining due to deforestation, pesticides, mine closures, unnecessary eviction, and even caving.
On the other hand, there are many reasons why it is undesirable to have them living in our buildings. First, their excrement and urine may contaminate food, stain ceiling and wall plasterboard, and give off a disagreeable odor. Second, they carry various ectoparasites such as the bat bug, tics, and fleas. Third, bats are known vectors of disease, including rabies.
If you see a bat flying during the day, be on your guard, it carries the rabies virus! If you believe you have been around a bat infected with rabies or have had direct contact or slept in a room with a bat, call Health Services in your province.
Rabies is a deadly disease in humans that must be reported to the authorities. This means that if you suspect that an animal is infected or that your animal has been exposed to rabies, you are required by law to report it to the governmental authorities in your province.
When you have a problem with bats, you must first evaluate the extent of the problem.
1st situation: One or two bats have entered through an open door or window or non-functioning chimney.
The easiest solution is to trap the intruders with a net or cloth. Always wear heavy leather gloves to avoid getting bitten. Like any wild animal that is afraid, bats may bite to defend themselves. If the bat is perched, you can place a container over it and carefully slide a rigid piece of cardboard or magazine over the opening to trap it. Avoid sudden movements and let it go outside the building if you are sure it has not had any contact with humans. If in doubt, put the bat in the freezer and call the Canadian Food Inspection Agency.
If there has been no contact with the animal, you can also leave doors and windows open to create an air current. Frightened bats will feel the current and go out. This method only works at night, as bats are inactive during the day, so be sure that all the lights are turned off.
2ne situation: A small group of bats is living under the eaves of your roof (exterior). What should you do?
In most cases, bats, most often males, will use this site only temporarily because they prefer warmer shelters. In certain cases, one can use polypropylene netting if they persist in roosting under the eaves.
3rd situation: A large colony of bats is living in a school, attic, church, etc.
This type of situation can be very complex. We always advise calling in a professional for an inspection in situations of this kind. In some cases, blocking the openings where the bats get in is sufficient, but usually, follow-up is necessary.
In order to identify the openings used by the colony, you must pinpoint where they go in and out. The best time to observe them is at dusk when they leave the roost or at dawn when they return. It may take a number of days to find all the openings.
The best time to permanently block these openings is in the late fall (mid-October), once the bats have left to hibernate in caves or underground mines, or in early spring before the bats return. If it is impossible to do the work during one of these two periods, we recommend you wait until at least mid-August to partially block the openings, because before that, the young bats will not necessarily have left the nest and will die inside the walls, causing additional odor and insect problems.
To partially block the openings, attach polypropylene netting on three sides, leaving the bottom edge free so the animals can climb out from under the net in the evening. At dawn, however, they will not be able to get back in. The netting can thus be applied during the day when the bats are resting.
There are no miracle products or tricks for dealing with bats. Products like naphthalene and p-dichlorobenzene crystals may have a certain repellent effect, but they are not sufficient and the treatment must be repeated after just a few days. What's more, some people are very sensitive to the odor emanating from these products.
Even if you place spotlights in the attic, the bats will just relocate to another area. Installing fans to create air circulation, which these mammals abhor, can also have a repellent effect. In some cases, putting fans in the building from April to May will discourage bats from roosting in the building. Poisoned bait (rat poison) is useless because bats are insectivores. Moreover, they capture their prey on the wing, so even if you could poison insects, they would no longer be attractive to the bats once they were dead. Some claim that ultrasound works to repel and disperse bats, but so far, no ultrasound device has truly proven its effectiveness.
Once the bats have been expelled, it is very important to clean the soiled surfaces well and remove all trace of the bats from inside the building. Odors left by a former colony of bats may attract a new one. You must also clean up any excrement. It is recommended that you wear a mask and appropriate clothing for this type of work. You may choose to call on specialists to do the job.
4th situation: Bats gather around exterior lights.
They are attracted to the insects that fly around lights at night. The easiest way to get rid of them is to shut the lights off for several days. The bats will go elsewhere to find food
- Call 811 (Info-Santé)in Québec or another health service in your province if you touch or are touched by a bat or have slept in a room with a bat in it
- Get air flowing by opening doors and windows to encourage the bat to leave
- Call a professional if a colony comes to roost in the attic
- Plug up any opening wider than 1.25 cm (1/2 inch) in late fall
- Use yellow incandescent bulbs outdoors (such as Philips Bug-A-Way) instead of soft white ones to minimize attraction of night flying insects