Bats are unique mammals known for their ability to fly. They navigate the night sky with agility, often accessing seemingly inaccessible spaces. Their presence can sometimes lead to questions about how they manage to enter confined areas. Understanding how bats achieve this feat reveals insights into their biology and behavior.
The Flexibility of Bats
The ability of bats to squeeze through small openings stems from several biological features. Unlike other mammals, their ribcages are not rigidly structured, allowing for compression of their bodies. This enables them to reduce their overall profile and navigate tight spaces. Their skeletal system is also adapted, featuring slender, lightweight bones that are less dense than those found in most other mammals.
While not hollow like bird bones, these lighter bones contribute to their agility without sacrificing strength. Bats possess mobile joints throughout their wings, including the elbow and wrist, which provide flexibility. Some bat species also exhibit flattened skulls, an adaptation that facilitates entry into narrow roosting sites. These combined anatomical traits allow bats to contort their bodies and pass through openings that appear much smaller than their actual size.
Common Entry Point Sizes
Bats exhibit an ability to enter structures through small gaps. Many species can fit through openings as narrow as 3/8 of an inch, which is roughly the diameter of a pencil or a dime. Some smaller microbat species can even navigate through gaps as tight as 3 millimeters. This feat is possible because bats do not create these openings; rather, they exploit existing structural vulnerabilities in buildings.
Homes often present potential entry points for bats due to construction gaps or wear over time. Common areas include loose or damaged roof edges, missing shingles, and gaps around roof tiles. Soffits and fascia boards, particularly where they are loose or have construction gaps, frequently serve as access points. Unscreened or damaged vents, such as attic, gable, ridge, and chimney vents, are also common avenues for entry. Small cracks in foundations, gaps around utility lines, and deteriorating mortar joints can provide sufficient space for bats to squeeze through.
Preventing Bat Entry
Preventing bats from entering a home involves inspecting the exterior and sealing potential access points. Homeowners should survey their property for gaps as small as 3/8 of an inch, paying close attention to areas like rooflines, soffits, fascia boards, and vents. Evidence such as greasy rub marks or guano around openings can indicate active entry points.
Sealing these gaps requires appropriate materials. Small cracks can be filled with weatherproof caulk. For larger openings, such as unscreened vents or damaged roof sections, durable materials like 1/4 inch or 1/2 inch wire mesh (hardware cloth) are effective. Expanding foam can also be used, but avoid applying it directly where bats are actively moving, as they can become entangled.
Timing is key for bat exclusion. Exclusion is best performed in late summer to early fall, after young bats are capable of flight. This avoids trapping flightless pups inside, which can lead to odor issues and distress for the colony. If bats are already present, one-way exclusion devices can be installed at active entry points, allowing bats to exit but preventing their return. For extensive bat problems or if exclusion is needed during maternity season, contacting a licensed wildlife control professional is recommended.