Bats are nocturnal mammals known for their unique ability to navigate and hunt in darkness. Many wonder what sounds might deter them, especially when bats roost in unwanted areas. Understanding their sophisticated use of sound provides insight into effective and humane bat management.
How Bats Hear and Communicate
Bats possess a sensory system called echolocation, which allows them to “see with sound.” They emit high-frequency sound pulses and interpret the echoes that bounce back from objects. This process provides detailed information about an object’s size, shape, texture, distance, and even movement.
The sounds bats produce for echolocation are ultrasonic, beyond the range of human hearing. While humans hear up to 15-20 kilohertz (kHz), bat calls range from about 9 kHz to 200 kHz. Most insect-eating bats use frequencies between 20 kHz and 60 kHz. Their hearing is highly sensitive, enabling them to detect objects as fine as a human hair.
Sounds Often Claimed to Deter Bats
Considering bats’ reliance on sound, many commercial products claim to deter them using auditory methods. The most common of these are ultrasonic sound devices. These devices are designed to emit high-frequency sounds that are inaudible to humans but are theorized to be disruptive or irritating to bats.
The underlying idea is that these ultrasonic emissions will interfere with a bat’s echolocation system, making it difficult for them to navigate or find food. Some believe these sounds cause enough discomfort to drive bats away from an area. Other high-frequency noises or even certain types of white noise are also sometimes suggested for bat deterrence.
Do Sound Deterrents Actually Work?
Despite claims, scientific evidence indicates that ultrasonic and other sound deterrents are largely ineffective for long-term bat control. While bats might initially react to sudden or unfamiliar sounds, they often become accustomed to constant noise. This adaptation means any temporary startling effect rarely provides a lasting solution.
A significant limitation of ultrasonic devices is the rapid attenuation and limited penetration of high-frequency sounds. These sound waves do not travel far and are easily blocked or absorbed by physical barriers such as walls, furniture, or vegetation. Consequently, a single device or even multiple devices often cannot cover an entire area effectively. Research has shown mixed results, with some studies finding only temporary reductions in bat activity and others reporting no significant impact.
Effective and Humane Bat Deterrents
Given the ineffectiveness of sound-based methods, more reliable and humane strategies are necessary for managing bats. Bats are protected by law in many areas due to their ecological contributions, such as consuming insects and agricultural pests, and aiding in pollination and seed dispersal.
The most effective approach for removing bats from structures is exclusion. This involves identifying all potential entry points into a building, which can be surprisingly small—some bats can fit through gaps as tiny as 3/8 of an inch. One-way exclusion devices, such as nets or tubes, are then installed over active entry points. These devices permit bats to exit the structure to forage but prevent them from re-entering.
After all bats have left, typically after several nights, the exclusion devices are removed, and all entry points are permanently sealed. Exclusion should occur outside the bat maternity season, usually mid-April to mid-August, to avoid trapping flightless young inside. Due to the complexity and legal protections surrounding bats, consulting a professional wildlife control specialist for bat removal is often recommended. Providing alternative roosting sites, such as bat houses, can also encourage bats to relocate to a more suitable area.