Bats in Your Building?

Do not panic; this is exciting. Bats are not the horrible monsters popular culture make them out to be. In fact, bats are nature’s pesticide and save the agricultural industry billions across North America. They also protect you from mosquitos and other pesky insects. Don’t be fooled, the 19 species of bats found in Canada all eat insects, NOT blood! So no need to be scared of bats.

Roost sites play a major role in the survival of all bats by providing thermal regulation, shelter from weather and predators and represent locations for social interactions. It is quite normal for some Canadian bat species to roost in buildings. The most common are the Big Brown Bat (Eptesicus fuscus), the Little Brown Myotis (Myotis lucifugus), and occasionally the Northern Myotis (Myotis septentrionalis). In British Columbia, there are two additional species of bat that could roost in homes: the Yuma Myotis (Myotis yumanensis) and the Townsend’s Big-Eared Bat (Piecotus townsendii).

CWF has spent several years studying bat roosting behaviour and ways to mitigate impacts to both bats and humans when they’re found roosting in a building. As a result, we have created a comprehensive guide.

1. Bats destroy will the house. FALSE. Unlike rodents who chew wires and tear apart siding, the only damage bats inflict on your dwelling is a buildup of guano and urine. This can be easily remediated with a plastic ground sheet, changed out every once in a while.
2. Bats will transmit diseases to my family. UNLIKELY. Rabies is top of mind for many people when it comes to bats. All mammals can contract and transfer rabies – not just bats. Cases involving bats and rabies in Canada are rare. More people are killed by lightning in a single year in Canada than by rabies in the last 50 years. However the disease is extremely serious so people should consult a medical professional for any known or suspected wild animal bite or scratch. Histoplasmosis is the other health concern with bats. It is a lung infection that is often associated with bat guano, but the spores that cause this infection naturally occur in soil in only in a few parts of Canada. Bat and bird droppings provide an environment for the spores to grow. Symptoms typically go away on their own or can be treated with medication. With decaying organic matter in confined spaces, whether bat, bird or mouse droppings, people should always wear protective equipment.
3. Bats will invade my house! FALSE. The good news is bats will have only one (sometimes two) pup per year, meaning they won’t rapidly increase in numbers. You can prevent bats from entering inside your living quarters by sealing spaces in floor joists and other entry points between roost and human living spaces. Bats can fit into small space sometimes making this difficult, so homeowners may have to hire a professional, and may need to resort to an eviction.

Did you know that eviction is not the only option? Unless bats are causing health problems to human occupants, it’s perfectly good to leave maternity roosts and established long-term hibernacula in place (especially for at-risk species). The site can be retrofitted to make the roost more attractive to the bats and decrease – or even eliminate – the frequency of interactions between the roosting bats and the landowner. Safety and health of the landowner is most important and there are ways to improve the roost that promotes survival and minimizes health impacts for humans.

Here are some tips to deal with guano:

1. Place a plant potter where the guano usually falls, or place a shelf or gutter along the wall below the night roost to catch the guano before it falls.
   --Keep the guano as it makes for an excellent fertilizer.
   --Accumulated guano can be removed annually.
2. Some wildlife service companies will clean it up for you. Contact your local provider to find out pricing.

If there are bats in your home and they are not causing major problems, or if the risks of evicting them (i.e. contributing to their extinction) outweigh the positives, please consider the points above. Remember, unlike rodents, bats are very slow at reproducing, typically having only a single pup per year.

People’s health and well being is of course of utmost importance. In a situation where a bat colony becomes problematic, a homeowner may choose to evict them from a roost or hibernacula. If you must carry out an eviction, it is extremely important to consider the bat’s life-cycle in order to ensure their survival and that no bats are trapped inside your home.

Although there are plenty of misconceptions surrounding bats, risks like rabies and histoplasmosis are legitimate concerns and it is important for homeowners to avoid direct contact with bats and feel they are safe in their own home. While evicting a bat colony will eliminate these risks to humans, improper management of the colony can pose devastating risks to local bat populations, and since some bats that may be found in buildings are legally listed as threatened and endangered provincially and/or federally these situations need to be handled with caution to prioritize the wellbeing of both humans and bats.

Females especially rely on established good quality maternity roosts to give birth and raise their pups year to year, so evictions from these maternity roosts may be particularly harmful to the colony. Additionally, the number of high-quality roost sites may be declining due to landowners resorting to evicting bats from their homes instead of managing them in place and so, unless a bat colony becomes problematic for the homeowner’s health, safety or well-being, an eviction should be a last resort.

If you are wondering about evicting bats, our guide to managing bats in buildings will walk you through these steps:

• Determine if the bats are causing major problems and the pros/cons of eviction.

• Bat houses can act as an alternative roost, but there are specific factors, in addition to general guidelines, that may make them more favorable for the bats.

• Figuring out which species is within the building and where, its status, myths and misconceptions, will allow for an informed decision on how to proceed.

If after weighing the pros and cons and having been educated on the realities of sharing a space with bats, it is decided that removing the bats is the best course of action, there are specific steps to carrying this out.

• Proper timing of an eviction is essential to ensure flightless pups are not blocked inside the building and that the colony has left for the winter. Evictions are best done March-April and September-November. And only in the winter if you can be sure the bats are not overwintering inside the building.
• Identification of the species of bat that are roosting in the home is ideal prior to an eviction or exclusion. Little brown myotis will leave their summer roost (ex. a building) to overwinter in caves; however, big brown bats are able to overwinter in buildings.