Far from being pests, all species of bats found in BC are voracious insect predators. Bats eat up to half their weight every night in moths, mosquitoes, beetles, crickets, grasshoppers and flies. A single little brown bat may catch up to 600 insects an hour.
There are 16 species of bats in the province and all are protected under the Provincial Wildlife Act. Most species are dark brown with short ears and small bodies about the size of mice. Wingspans range from 20 to 42 centimetres (about nine to 16”). The most common species found in buildings are the little brown bat (Myotis lucifugus) and big brown bat (Eptesicus fuscus), which thrive throughout the province, and the Yuma myotis (Myotis yumanensis), which is found only in the southern part of the province.
Bats enter a building for a variety of reasons, including simply flying in by accident. They may use buildings as a temporary, daytime roost, as a nursery to rear their young or, occasionally, as a hibernation site. Attics are a favorite bat refuge.
Like other mammals, bats can carry fleas, mites and ticks; in rare cases, they contract rabies. Unlike other mammals with rabies, however, they tend to get sick and die before becoming aggressive. According to Agriculture and Agri-Food Canada, which tests about 100 injured, sick or dead bats annually, no one has contracted rabies from a bat in BC.
Health Risks Relating to Bats
Histoplasmosis is an airborne disease caused by a microscopic fungus that occurs in soil and in the nitrogen-rich droppings of birds and bats (Tuttle and Kern 1981, Greenhall 1982, Fenton 1992). A dry cough and other flu-like symptoms are the usual signs of histoplasmosis, which is often mistaken for influenza. While histoplasmosis often does not produce any symptoms, severe symptoms such as high fever, problems with vision and life-threatening complications occasionally do occur.
How to Evict Bats from Your Home
The most effective long-term solution for evicting bats from roosting or hibernating in one’s home is to prevent them from getting there. If they are already present, their place of entry must be sealed while the bats are gone.
There are several ways to locate the entry and exit points. Keep in mind that some bats are small and the ones that use attics and other buildings may enter through a crack of a half inch or less.
Try watching in the evening around dusk. See if you can spot the bats emerging, and mark or remember where the holes are. Another way is to enter the roosting place during daylight hours. Look for light leaks coming in from the outside daylight. Still another way is to turn on the lights or place lights in the roost and then look from the outside for light leaks after dark.
Once the holes are located they must be sealed in some way, whether it be by caulking, wood strips, or even steel wool placed in the holes. Do not do this until late July when the young are able to fly and are leaving to feed.
Another means of exclusion is to hang half-inch polypropylene bird netting directly above the exit holes. The netting should extend at least one foot to each side and below the hole. The sides and tops of the netting should be attached to the building but the bottom should be allowed to dangle free so that bats leaving the building can find their way out by dropping down to the open end of the netting. After about two or three nights, all the bats will have left the building and the entrances can be plugged permanently.
Cleaning Up After Bats
Once the bats have been excluded from the roost area should be thoroughly cleaned as bat droppings can create a strong odour. This odour may also attract bats if new openings develop in the structure. Use caution cleaning the area to avoid contracting histoplasmosis. Histoplasmosis is a respiratory infection caused by inhaling fungal spores which may grow in bat droppings. This fungus is widespread in soils throughout the world. In this country it is most prevalent throughout the Mississippi and Ohio River valleys and primary sources of infection are the droppings of starlings, pigeons and poultry. Although most people who contract histoplasmosis have few if any symptoms or problems, some people develop serious respiratory conditions.
When cleaning up bat droppings, wear a tight fitting respirator that will filter particles as small as two microns. Dampening the droppings before cleaning them up will help decrease the spread of any spores. The droppings should be sealed in plastic bags for disposal. The area should then be cleaned and disinfected with a solution of one part household bleach to 20 parts water. Clothes worn while cleaning should be washed immediately. If for any reason you don’t feel comfortable performing this task, call a professional.
Install a bat house! There is nothing greener than keeping the bats around to help keep the number of mosquitos down.