Signs of a Bat Infestation in the Attic

Photo by: Bigstockphoto
Photo by: Bigstockphoto

Bats are small, nocturnal mammals that live in caves, trees, cliffs and rock faces. But because of their dwindling natural habitat, bats have taken on to living in man-made structures, such as houses, barns, churches, and even bridges.

Bats roosts according to the season. During the winter season, bats will hibernate and in summer, only the females with younglings will roost in large groups. Male bats will roosts in small numbers in preparation for the mating season.

Bats are always on the move throughout the year and sometimes, they will make their way into your home, like the attic. And for most homeowners, finding roosting bats in the attic is not a pleasant discovery since bats do carry contagious diseases, including rabies. Unfortunately, most homeowners are not aware that bats have invaded their homes until it is too late. So how do you know that your attic is infected with bats? Let’s find out:

Bat Droppings

Bat guano or droppings are the first sign that bats are living in your attic. The bat guano is similar to mouse droppings but is quite black and crumbly. If you look at bat droppings closely, you are bound to see undigested fragments of insects they’ve been eating like moths, butterfly wings, cockroaches, etc. Usually, the bat droppings are found under a bat’s feeding perch.

Bat guano piles up very quickly and the odor will emanate to the rest of the home even if the affected area is confined to the attic. The guano will produce a rancid ammonia stink as it decomposes. Once the guano piles high enough, it will start to rot and collapse. The guano carries with it disease-causing microbes that could make pets and humans sick.

Bat Urine

Another telltale sign of a bat problem is bat urine. Just like the droppings, bat urine will generate a rancid ammonia stench that will quickly spread to the rest of the home. Because bats are perched high on a structure, the bat urine will trickle down a wall, so you cannot miss it. Removing the dried up, trickle of bat urine is very hard because the liquid leaves a persistent stain that does not go away completely no matter how hard you scrub the surface. Worse, bat urine causes corrosion on metal surfaces.

Grease Stains and Scratch Marks

On the entrance of a bat roost, you are bound to see dark grease stains and scratch marks. Bats have very long claws and they end up scratching around the entrance of their perch.

Stray Baby Bats

A clear sign that you have a severe bat problem is finding a stray baby bat or two inside your home. Baby bats are not always the best flyers so they end up losing their way into their roosts. Sometimes, the baby bats lose their grip while high up on the perch and they end up in a hole that leads to your ceiling. Eventually, they will end up inside your home. Again, bats carry diseases, even younglings so it is not a good idea to hold the bats without using the right gear.


Bat screeches are hard to miss especially during daytime when these animals are in their roost sleeping. The chirping gets worse on hot days when their roosts become very warm.

If all the signs you found indicate a bat roost in the attic, we do not recommend exterminating the bats on your own. Killing the roosting bats will not stop other bats from coming into your home. Getting rid of any pests should always involve humane methods. We recommend calling a professional bat exterminator to handle the problem using the right tools and techniques.