How to Identify Bat Droppings (Bat Guano)

During any given home inspection, I always keep my eyes peeled for bat guano. Because bats tend to be quiet little stowaways, they often go undetected by homeowners. When I find bat droppings during an inspection, it tends to be in the attic, often accompanied by bats, but this isn’t always the case. Below is a little more information on bat guano, and how you can identify it:

To the naked eye, bat guano frequently resembles the droppings of mice, which look a lot like black grains of rice, but while mouse and bat droppings appear very similar, a closer look can help to identify their differences. Because bats and mice have very dissimilar diets (mice eating vegetable material, and bats eating insects), their droppings differ.

The first notable difference is that unlike mouse droppings, bat guano has a tendency to crumble like dust when touched. Secondly, bat droppings contain the elytra (wing cases) of insects, so in sunlight guano often appears to shimmer or sparkle, or when crushed, you can often see these insect fragments more clearly. Lastly, because bats defecate before they enter your home, and below where they roost for the day, bat guano tends to be clustered, while mouse droppings tend to be scattered.

Be aware that most bats do not carry rabies, but a build-up of their droppings and urine is a quick process, and is definitely not good for your home.