Managing bats in buildings

If bats are roosting in an area that isn't interfering with human activity, consider leaving them undisturbed. They won't destroy wood, wires or insulation.

If a bat has entered the living area of your building, try getting them to leave on their own by:

• Closing interior doors
• Opening outside doors and windows
• Turning off the lights

A sleeping bat inside a house can be safely picked up:

• Always wear thick gloves if handling a bat
• Use a pillowcase or a box to gently trap the bat
• Place the bat outside in a safe spot, out of reach of cats or other predators. Select a place where the bat can swoop down to take flight (for example, high on a porch, the top of a vehicle, or a tree branch)

Bats are protected under the Wildlife Act. Certain actions are illegal and ineffective for bat removal.

• Do not use pesticides
• Do not play loud music
• Do not use ultrasonic devices
• Do not scatter mothballs
• Do not set up bright lights

Preventing bats from entering buildings

Prevent bats from entering by keeping up with building maintenance. Do regular inspections to find and block any entrance points under eaves or around pipes, vents, doors and windows. Bats can enter through a dime-sized hole or crack. Make sure there are no bats inside before blocking entrance points.

If bats are already present inside the building and living with the bats in not an option, you will have to evict them before blocking any holes.

Step 1: Find out where bats are getting in

• Check areas a meter or more off the ground, near wall and roof joints and under loose chimney flashing
• Check for unscreened louvres (window shutters) and air intakes, gaps in the fascia boards, along the eaves and near dormer (roof) windows
• Listen for squeaks
• Look for brownish oil stains on walls. This is evidence that they've been squeezing through small cracks
• Check for bat droppings (guano) on the ground. Bat guano is similar to mouse droppings in appearance
• At dusk, watch for bats flying out of the suspected entrance as they leave to find food

Step 2: Evict the bats and prevent them from re-entering

In spring or fall, install a one-way escape hatch and leave it in place for a week or two to ensure bats have left before fully blocking entrance points.

You can use commercial ‘bat cones’ or you can make a one-way escape hatch.

To make a one-way escape hatch:

• Use polypropylene bird netting or fly screen to make a large flap over the escape hole
• Use duct tape or staples to attach the netting at the top of the exit only 
• The netting should hang loosely and extend at least 20 cm on each side and below the exit point

For more guidance visit Excluding Bats from a Building.

 

Sometimes it's not possible or not necessary to evict bats. For example, they frequently roost under wood shakes on roofs or under cedar siding. In these cases, the best option is to learn to live with the bats, especially since they don’t damage the building. Hosting a bat roost is also beneficial to the environment.

Follow these tips to live with bats in buildings:

• Ensure that there is no way for bats to find their way into human living quarters
• Install flooring or lay down plywood in your attic space to cover ceiling joists
• Cover the flooring with plastic for easy cleanup and removal of bat feces (guano)
• Limit the number of entry points used by bats by blocking undesirable access points
• Do any repair work and a seasonal cleanup from October to March, when bats have left their summer roosts

Be careful not to disturb a bat hibernation site. This can cause them to burn off valuable stored energy and die of starvation.

Bat feces (guano) may be stinky but it also makes an excellent fertilizer for the garden.

In extremely humid environments, guano dust can carry a disease organism that causes a lung infection called histoplasmosis. This is rare in the Pacific Northwest, although it is common in other regions. Always wear a respirator mask when investigating or cleaning a bat roost in a confined space.