Bats are the only flying mammal in the world. They are very beneficial because they can eat over 500 flying insects, (such as mosquitoes) per hour, all night long. Over 40 species of bats live in North America.

Bats need a safe place to roost in the daytime, and much of their natural habitat is dwindling. There is a safe, effective and responsible way to deal with the problem.


Like other mammals, a small percentage of bats contract rabies (figures issued by the Health Department may show a higher percentage since sick bats are easier to catch than healthy bats). Exposure to the rabies virus is remote if contact with bats is avoided and pets are properly vaccinated.

Histoplasmosis is an airborne fungus disease that can grow in pigeon and bat droppings (guano), especially in moist environments.

Human inhalation is usually the result of stirring up dust that contains contaminated fungus spores, therefore it is not recommended to clean up guano unless there is a serious odour or health problem. Guano should only be cleaned up by trained personnel with the proper safety equipment.

Bats are host of ectoparasites such as bat bugs (close relative of bed bug). These are usually host-specific and rarely bite humans or pets. Ectoparasites can be controlled by an insecticide treatment to the roost after bats have been evicted.


Humans object to the bats squeaking, scratching and crawling in attics and walls stains and odours caused by urine and guano. Most bat complaints occur in July and August when bats enter (a dime-sized hole) via overhangs, eaves, under screened vents, and end construction gaps, chimneys and open windows. Some may actually enter the building interior due to getting lost seeking a preferred temperature zone.

Biology and Habits of House Bats

Bats are nocturnal (active at night) and have A 6 to 12’’ wingspan. They are insectivores. They usually breed in fall or winter. Pregnant females congregate in maternity colonies until birth occurs between April and July. There are usually 1 or 2 young in a litter, and they will begin to fly at 4 weeks of age.

Little brown bats commonly invade structures in the spring and summer, while big brown bats use buildings year-round for raising young and hibernation.


Exclusion is the number one priority in bat Management. Thorough exclusion of all holes larger than ¼’’ is needed at all potential openings, especially in the top half of the building. Control should be left up to professionals.


Poisoning bats is illegal as they are a protected species. Repellants are generally ineffective and may actually drive the bats further into the structure.


Bats, despite their obvious value, are Unjustifiably persecuted. Public education on bat conversation and responsible control methods are needed.

For multi units

The Ottawa Health Unit reports a 5% increase in rabies-tested bats in the Ottawa area.

  • Bats return year after year to their roosts. Maternity colonies double year after year.
  • Key areas where bats enter are: – 1/4’’ gap and above
    • Where soffit meets siding
    • Construction Gaps
    • Roof Flashing
    • Roof Vents
    • Under shingles where it meets the Fascia
    • Fascia, Soffit
    • Around exterior light fixtures
    • Conduit holes
    • Wall vents (Stove, Dryer, Bathroom)
    • Roof Soffit Interfaces, etc.

Sealing one unit in a row of units will not solve or deal with the problem. Bats will just move. Multi Units share walls, soffits and roofs. Bats follow air flow. Air flow is key.

There are legal ramifications of dealing with bats in multi unit townhomes when only sealing one unit. For instance, ‘‘ Child bit by bat’’, who is liable? The contractor following the managements orders? Or the management company? The answer is, the management company.