Are Bats in my House? Tips to determine the answer without using a ladder

Homeowners should consider the possibility that bats are residing in the home when they encounter one or more of the following signs:

• high-pitched clicks,
• scratching noises around walls or ceilings,
• persistent but unusual odor,
• sightings of staining (Figure 1), 
• sightings of droppings in the same location over time (Figure 2),
• discovery of a bat in the living space on two different occasions during the summer or once during the winter. “Living space” refers to the human-occupied portions of the house as distinguished from walls and attic.

BATS IN THE LIVING SPACE

Bats encountered in one’s living space pose specific health concerns, namely possible rabies exposure to loved ones and pets. While estimates are that less than 0.5 percent of all Montana’s bats carry rabies, do not assume the bat in the living room is rabies-free. Therefore, whenever a bat is found in the living space, capture the bat (without damaging its brain, see “How to Capture a Bat”) and do not release it without consulting with the local health department and/or veterinarian. Contact the health department for exposure to people and a veterinarian for exposure to pets. Do not assume that bites by bats are easily identified. Bats have needle-like teeth whose marks are difficult to see even when the location of exposure is known (Figure 3).

If clues suggest there may be bats residing in a home, the next step is to confirm their presence using one, or preferably more, of the following options. 

Option 1. Perform a bat watch. On a clear night with low wind (under 30 mph), go outside around dusk. Stand far enough away to see the house silhouetted against the light-blue, pre-nighttime sky. Recruit friends and family to take positions around the house. Watch carefully for bats to appear against the blue sky. The first person to see a bat will help narrow the area where the bat may have emerged. On subsequent nights confirm the location. Note that bats may have two or more exits from a house.

Option 2. Inspect the attic. Before entering an attic, be sure to anticipate the possibility that entering the attic will disturb droppings. Place a drop cloth below attic entrances to catch falling debris. Wear appropriate safety equipment before opening the hatch, including an N-100-rated respirator, eye protection, long-sleeve shirt and pants, socks and shoes, and leather work gloves. Be healthy enough to wear a respirator and have training in its proper use. 

With a strong flashlight, look for bat droppings on the attic floor and for bats roosting at the vents or ceiling. Consider that bats may be in the walls, and thus not visible. Do not assume that bats are absent if signs of activity aren’t obvious.

Option 3. Look for staining. With a pair of strong binoculars (8x or higher), inspect for staining at typical bat entry points, such as:

• under roof overhangs where wood may be warped, shrunk, or rotted,
• around loose or unscreened vents, 
• under loose flashing, 
• at louvers, eaves, or cornices, 
• under loose roofing or siding, 
• around windows, 
• around chimney pipes,
• where wiring and water pipes enter a building. In other words, whenever there is a joint, seam, or gap in the structure that may have opened enough to allow bat entry. 

HOW TO CAPTURE A BAT

1. Restrict the potential movement of the bat by closing doors, closets, and drawers. If the bat is flying, wait for it to land. Avoid letting the bat get out of sight.
2. Wear thick leather gloves.
3. Get a large-mouthed Tupperware-style container with an opening around five inches with matching lid.
4. Approach the landed bat from one side and place the container over the bat. 
5. Slide a piece of cardboard or stiff paper between the wall or surface and the bat, trapping it inside the container.
6. Replace the cardboard/stiff paper with the container’s lid and tape it for extra safety.
7. Contact the county health department for guidance on animal testing and rabies vaccinations.

If a house is believed to have bats, read the bat control bulletin available at https://agr.mt.gov/Vertebrate-Pests or contact the author at svantassel@mt.gov or 406-538-3004.