Bat Removal

Bat Removal and Exclusion in New York Homes

January 24, 2025·12 min read

Bats in New York occupy a unique legal position among nuisance wildlife: they are protected under both federal law (the Migratory Bird Treaty Act, which covers insectivorous bat species) and New York State law, and killing them — even inside your own home — is illegal. At the same time, bat colonies in residential structures create legitimate health risks and significant structural contamination. Understanding the legal framework and proper exclusion process is essential for any New York homeowner dealing with a bat infestation.

New York's Bat Species

Two species account for the vast majority of residential bat conflicts in New York:

Little Brown Bat (Myotis lucifugus)

The little brown bat is the most common roosting species in New York structures. Colonies range from a handful of individuals to several hundred. Little browns are colonial roasters — females gather in maternity colonies in warm attic spaces to give birth and raise young. A single colony in a suburban Long Island or Westchester home can produce hundreds of pounds of guano over a decade, requiring full attic remediation.

Little brown bats are currently listed as a Species of Special Concern in New York due to population losses from white-nose syndrome (Pseudogymnoascus destructans), a fungal disease that has killed millions of bats across the northeastern United States since 2006. This protected status reinforces the no-kill mandate.

Big Brown Bat (Eptesicus fuscus)

The big brown bat is slightly larger, more solitary, and more tolerant of human-modified environments. Big browns are more commonly found in smaller groups — often 5–20 individuals — and are more likely to roost in wall voids, behind shutters, and in tight spaces under roofing materials. They are also more likely than little browns to enter living spaces through gaps around light fixtures, plumbing penetrations, and HVAC registers.

Federal and State Legal Protections

The Migratory Bird Treaty Act (MBTA) extends federal protections to many bat species, prohibiting their harassment, harm, or killing without federal authorization. In New York, this is reinforced by state regulations that require:

• Exclusion-only removal: No lethal methods are permitted. The only legal removal method is one-way exclusion — allowing bats to exit but not re-enter.
• Seasonal restrictions: Exclusion is prohibited from June 1 through August 15 (maternity season). During this period, flightless pups are present and cannot follow their mothers out through exclusion devices. Sealing during the maternity season traps young bats inside, where they die, creating a severe odor problem and potential rabies exposure risk from dead animals.
• Legal exclusion windows: Spring (mid-April through May 31) and late summer/fall (August 16 through October). Many professionals prefer fall exclusion because the colony is fully mobile and there is more time before winter hibernation prevents further work.

Health Risks: Rabies and Histoplasmosis

Bats carry two significant health risks for New York residents:

Rabies

Bats are the most common source of human rabies exposure in New York State. A bat found in a room with a sleeping person, an unattended child, or an intoxicated person must be treated as a potential exposure — bat bites are small enough to go unnoticed, and rabies is uniformly fatal without post-exposure prophylaxis (PEP). The New York State Department of Health recommends a low threshold for initiating PEP.

If you wake up with a bat in your room, do not release it if at all possible. Contain it (using a coffee can and cardboard lid, or thick gloves) for rabies testing, or contact your county health department for guidance. Do not handle a bat with your bare hands under any circumstances.

Histoplasmosis

Bat guano supports the growth of Histoplasma capsulatum, a fungus that causes histoplasmosis — a respiratory illness ranging from flu-like symptoms to severe pulmonary disease in immunocompromised individuals. Guano accumulations in attics must be removed using full respiratory protection (P100 respirator or PAPR), Tyvek suits, and wet-removal methods that prevent spore aerosolization. Do not attempt to shop-vac bat guano — this is a health hazard.

The Bat Exclusion Process

A properly conducted bat exclusion involves several stages:

1. Full exterior inspection to locate all active roost entry points. Bats can enter through gaps as small as ⅜ inch. Look for dark staining (guano and body oils) around potential entry points at eaves, ridge caps, roof-to-wall junctions, and behind soffits.
2. Interior attic inspection to assess guano accumulation, identify the primary roost area, and check for bat entry into interior spaces.
3. Exclusion device installation: One-way bat valves or exclusion netting is installed over active entry points during a legal exclusion window. These allow bats to exit but prevent re-entry. Exclusion devices must remain in place for a minimum of 3–7 days to allow all bats to depart.
4. Sealing of all secondary entry points with appropriate materials (caulk for hairline cracks, hardware cloth for larger gaps, stainless steel wool for irregular openings).
5. Removal of exclusion devices and permanent sealing of primary entry points.
6. Guano remediation: Removal of contaminated insulation, application of enzyme-based decontaminant, and installation of new insulation.

Common Entry Points in New York Homes

New York's housing stock creates specific bat entry vulnerabilities:

• Older homes (pre-1970): Deteriorated wood fascia and soffit boards, gaps at the junction of chimneys and roofing, and failing caulk at roof-to-wall flashing are the primary entry sources.
• Cape Cods and ranch houses (common in Nassau, Suffolk, Westchester): Poorly ventilated attics with ridge vents are a common bat entry point. Many ridge vents lack integrated screening and allow direct bat access.
• NYC brownstones and attached homes: Parapet walls, shared rooflines, and deteriorated mortar at chimney stacks are primary bat entry points. Coordinating exclusion with neighboring buildings is often necessary in attached structures.

Frequently Asked Questions