Calixa-Lavallée, a small rural municipality in the Montérégie region (Marguerite-D’Youville RCM) neighbouring Verchères and Contrecœur, is a peaceful, mostly agricultural environment, bordered by fields and wooded areas. This very rich landscape naturally favours the presence of bats which find an abundance of insects on which they feed every night. It was in this bucolic setting that a country home owner contacted our team after observing, on several consecutive evenings, bats entering and exiting through the junction between the wooden gallery and the vinyl shingle. The narrow space between the exterior cladding and the structure of the house had clearly served as a day roost for a well-established colony. Since bats are wildlife species protected by Quebec law, a methodical and humane intervention was necessary, without the use of any lethal substance.
Initial assessment and access mapping
Our technician from our team in Calixa-Lavallée carried out both a day and a twilight inspection. Sunset observation is an essential technique to accurately locate all active entry points: by seeing the bats emerge one by one at dusk, it is possible to map each opening used by the colony. This country residence, whose wooden structure dated from the 1970s, had several additional flaws: gaps between the rim joists, a partially peeled dryer ventilation joint, as well as a section of shingle lifted by the many freeze-thaw cycles of Quebec winters. A total of six potential points were identified during this inspection, two of which were considered to be the main entry points to the colony.
The attic, accessible through an interior hatch, was inspected in detail and did not have any significant guano: the colony therefore lived in the narrow space between the outer lining and the air barrier. This type of colonization is common in old wooden houses in rural Quebec and requires a well-adapted approach of exclusion, because this space is often continuous along the entire length of the façade wall, making confinement more complex than in an open attic.
Unidirectional exclusion and progressive sealing
After confirming that the calving period was over, our technician installed soft exclusion cones at the two main entry points. These devices allow bats to go out freely in the evening to hunt insects, but do not allow them to return when they return. All other secondary accesses identified were closed simultaneously, forcing the animals to use only the exits equipped with exclusion devices. This technique is widely recognized as the preferred method for human exclusion of bats, as it does not cause harm to the animals and respects their natural behaviour. For an overview of a similar intervention, see our project on a rural residence on the South Shore.
Our specialist also recommended the installation of a bat box in the wooded area adjacent to the property. This practice, which is becoming more and more widespread in the integrated management of protected species, provides animals with an alternative habitat in the immediate vicinity and considerably reduces the risk that they will seek to return to the home in the following seasons. Our team offers these additional recommendations with a view to sustainable and respectful cohabitation between humans and local wildlife.
Permanent sealing and prevention tips
Once the exclusion devices were removed after confirmation of the departure from the colony, the openings were permanently sealed with suitable materials. The shingle joints were redone with high-durability exterior caulking, the joist spaces were covered with heavy-duty galvanized wire mesh, and the dryer vent gasket was replaced with a check valve model. This caulking work at entry points is the lasting guarantee of a house that is well protected against any new colonization, whatever the season. Our extermination company provided the homeowner with a seasonal checklist to be completed each spring, including inspecting soffits, rack junctions and roof fans, to prevent future reinfestation. The follow-up carried out two months after the intervention confirmed that the house was perfectly free of bats, much to the relief of the owners. See our bat capture service for more information on all of our human exclusion methods in Quebec.