Bats in the House

📐 FIELD GUIDE ILLUSTRATION

Bat (Chiroptera) identification illustration with labeled anatomical features — PestControlBasics.com

Original illustration by PestControlBasics.com. Use the labeled features above to confirm your identification.

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PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

🔍 Identification

Big Brown Bat (Eptesicus fuscus): Wingspan 12-16 inches; most common attic bat in US.

Little Brown Bat (Myotis lucifugus): Smaller; colonial; often thousands per colony.

Signs of bats: accumulation of guano (small, dark, insectivorous pellets that crumble to dust — unlike rodent droppings); staining around entry points; chittering sounds at dusk.

🧬 Biology & Behavior

Colonial bats form maternity colonies in spring/summer. Big brown bats typically establish colonies of 20-300 in attics. Little brown bat colonies can number in the thousands. Pups born June-July cannot fly until August. This is why exclusion is prohibited in most states June 1 through August 15.

⚠️ Damage & Health Risk

Guano accumulation (health hazard — histoplasmosis fungus), urine staining and odor, structural damage, and rabies risk. Any direct contact between a bat and a sleeping person requires medical evaluation — bats can bite without the person waking.

🚨 If you wake to find a bat in a room where someone was sleeping, assume potential exposure and contact your local health department immediately about post-exposure prophylaxis (PEP).

🔧 DIY Treatment

Bat exclusion requires one-way exclusion devices installed at all entry points (typically 3/4-inch openings along rooflines). The exclusion window: late summer (mid-August through October) after pups can fly but before hibernation. All gaps sealed permanently after 5-7 days of exclusion devices being in place.

👷 When to Call a Pro

Bat exclusion requires knowledge of bat biology, state and federal regulations (many bat species are protected under state and federal law), and careful work at heights. This is one situation where professional wildlife control is strongly recommended.

❓ FAQ

Are bats dangerous?

The primary danger is rabies — bats are the most common rabies vector in the US, responsible for most US rabies fatalities. Any direct bat contact requires medical evaluation. Beyond rabies, bat guano can harbor Histoplasma capsulatum, a fungus causing histoplasmosis when dust is inhaled.

Are bats federally protected?

All US bat species are protected under the Migratory Bird Treaty Act (which covers bats in some interpretations) and many are listed under the Endangered Species Act. It's illegal to kill or harm most bat species — exclusion, not extermination, is required.

🦇 Bat