Signs of a Bat Infestation

Bats can be beneficial to the environment, but when they invade your home they can become a significant nuisance and health hazard. Identifying the signs of a bat infestation early is crucial to prevent property damage and minimize health risks. Here's what to watch for.

The 4 Key Warning Signs

1. Nocturnal Noises

One of the most noticeable signs is unusual sounds at night — scratching, chirping, or squeaking coming from your walls, ceiling, or attic. These sounds are often faint but persistent, indicating that bats are actively moving around inside your home near dusk and dawn.

2. Guano Accumulation

Bat droppings (guano) are a clear indicator of infestation. Look for small, dark pellets or staining near entry points, windowsills, or on attic floors. A concentrated area of guano almost always points to a primary entry or exit point. Importantly, guano can harbor the fungus that causes histoplasmosis — a respiratory illness — so avoid disturbing it without proper protection.

3. Strong Musty Odor

Bats leave behind a strong, persistent musty odor — especially in areas with poor ventilation like attics or crawlspaces. If you notice an unexplained unpleasant smell in your upper floors that intensifies in warm weather, bat urine and guano accumulation is a likely cause.

4. Oily Stains Near Entry Points

Bats repeatedly squeeze through the same gaps and cracks, leaving behind dark, oily stains from the oils in their fur. Look for smudges or discolorations around vents, soffits, fascia boards, ridge lines, and any gap larger than 3/8 of an inch.

What to Do Next

If you've identified any of these signs, take action quickly. Bat colonies grow, damage worsens over time, and Tennessee law restricts removal during maternity season (May through mid-August). Acting before that window opens is the smartest move. After professional removal, consider installing a Custom Bat House to give the colony a safe alternative roost and reduce the risk of re-entry.