Nearly 80% Notice Bat Infestations After Seeing the Animals Themselves, with Noise and Odors Among the Main Problems

As temperatures rise in spring, bats become more active. In Japan, the Japanese house bat, which can settle in private homes, is found nationwide. These bats enter buildings through small gaps and cracks, causing various types of damage. In reality, however, it is often difficult to notice that bats have taken up residence in a home. Many people feel uneasy because they sense an animal presence but cannot tell whether it is a bat or a mouse. BEST Inc., a company that addresses household concerns and is headquartered in Yokohama, Kanagawa Prefecture, has spent more than 20 years solving everyday problems. Its information site, Gaichu Gaiju Concierge, publishes accurate and useful information about pests and nuisance wildlife. The company conducted an original survey of people who had experienced bats living in their homes, collecting 167 valid responses. The survey found that many respondents realized bats had settled in their homes after seeing them flying. This release introduces what led people to notice bat infestations, the specific damage they experienced, removal methods, and costs. It is intended as a useful reference for people worried about bat-related damage. Survey overview: respondents were people across Japan who had experienced bats living in their homes; the survey period was February 25 to March 5, 2025; the survey was conducted in-house; responses were collected voluntarily online; valid responses totaled 167. About 80% noticed because they saw actual bats. The most common triggers for realizing bats had settled in a home were “seeing them outdoors, such as in a garden or on a balcony” at 49.7% and “finding droppings” at 44.9%. This was followed by “seeing them inside a room or hallway” at 31.1%. Many people have seen bats around their homes, but they may not simply be flying by; they may already be living nearby. It is not unusual for bats to rest on balconies or exterior walls near entrances and then slip inside. Many people also notice bats through droppings. This is likely because bats produce a large amount of waste and tend to defecate in specific places. Bat droppings are about 5 to 10 mm long and resemble mouse droppings, but they are dry, crumble easily, and often contain legs or wings from insects, their main food source. While mice leave droppings in various places, bat droppings are often found near areas where they can easily enter homes, such as under eaves or around balconies. If droppings are concentrated in one or two spots, bats may have settled there. The most troublesome bat-related problems are noise and odors. The most common types of damage were “wing sounds, movement noises, and calls were loud” at 25.8% and “bad odors from droppings were severe” at 22.2%, together accounting for roughly half of responses. Noise tends to occur from after sunset until around 10 p.m., when bats actively enter and leave their nests. If the number of bats increases, the situation can become serious enough to prevent residents from sleeping. As noted above, bats produce large amounts of droppings, which emit a distinctive odor similar to a mix of sewage and ammonia. The smell can cause stress and may also lead to physical symptoms such as headaches and nausea. The odor becomes especially intense from June to October, when temperatures and humidity rise. There were also a small number of health-related reports, including “allergic symptoms such as coughing or dermatitis” at 3.0% and “contracting an infectious disease” at 1.2%. Wild bats can carry parasites such as mites and lice and may also serve as vectors for dangerous infectious diseases such as histoplasmosis and Nipah virus. Never touch a bat with bare hands, even if you see one. Bats commonly settle in attics, gutters, and storm shutter storage boxes. The most frequently reported locations were attics at 37.7%, inside gutters at 21.6%, and storm shutter storage boxes at 21.6%. Bats prefer dark, damp environments where predators are unlikely to find them, and they can enter through gaps as small as 1 to 2 cm. Cracks in roof tiles, gaps between roofs and exterior walls, and gutter joints are especially vulnerable. Roofs and exterior walls often begin to deteriorate when a home is around 10 to 20 years old, so homes that have not been renovated for many years face a higher risk of bat entry. Storm shutter storage boxes naturally contain gaps due to their structure, making them easy entry points. If shutters are left open or closed for long periods, bats may settle in unnoticed, so regular opening and closing is recommended. Other reported locations included shutter gaps at 9.6%, outdoor air-conditioner ducts or piping at 8.4%, and vents or ventilation fans at 7.8%. Homes contain many places bats prefer, and after entering, they can move through walls and pipes to form nests in various areas. Once settled, they may form groups of at least 10 and as many as 200, sometimes spreading throughout a home without residents realizing it. Bats can be removed by homeowners themselves. Although bats may seem like mysterious creatures, about half of respondents said they removed them on their own. Repellent sprays for driving out bats are sold at home improvement stores and online, and they are essential items for DIY removal. Masks, goggles, and rubber gloves should also be prepared to prevent infectious diseases and allergies. Other needed items include a handheld vacuum and alcohol disinfectant for cleaning and disinfecting nests with accumulated droppings, caulk and a caulking gun for sealing entry routes, perforated metal sheets, and repellents to prevent reentry. However, professional help is recommended when bats are in places that are difficult to enter, such as attics or crawl spaces, or when work is required at heights of 2 meters or more. Even with protective gear, there is still a risk of infection or allergic reactions. If small children or elderly people live in the home, it is better to have professionals handle removal. The typical cost of DIY bat removal is 1,000 to 5,000 yen. The most common costs were “1,000 yen or less” at 36.3% and “1,001 to 5,000 yen” at 28.8%, together accounting for more than half of responses. Given that most people removed bats themselves, this cost range is understandable. With repellent spray costing about 1,000 yen per bottle and a dust mask costing about 3,000 yen, many people appear to be using only minimal equipment. Hiring a professional for bat removal costs about 42,000 yen. For example, bat removal from the attic of a 30-tsubo house, assuming an area of 10 square meters and an inspection hatch, costs 19,800 yen for repellent liquid spraying, from 500 yen per location for sealing entry routes, and 22,000 yen for cleaning including disinfection, for a total starting at 42,300 yen. Actual costs vary depending on where bats have settled and where they entered. If bats are in an attic or underfloor area with no inspection hatch, an additional installation fee of 8,800 yen may be required. Work details may also change, such as using a smoke agent instead of repellent liquid to drive the bats out. Because bats can move inside residential walls and settle in multiple places, affected homeowners should first request an on-site inspection and estimate. If left untreated, bats can cause noise, bad odors, and serious health risks for residents, so professional removal is recommended. In summary, although bats are often imagined as living in forests or caves, they appear in residential areas at night, settle in private homes, cause various forms of damage, and threaten residents’ daily lives. Many people realize bats have settled in their homes after seeing them enter the house or spotting them indoors, while others discover them through large amounts of droppings. Commercially available products can be used for removal, but bats may not be completely driven out or may settle in another place without residents noticing. Bats may also carry parasites or infectious diseases, and contact during removal can lead to serious health harm. Those troubled by bats at home and seeking reliable, safe removal should consider hiring specialists. Gaichu Gaiju Concierge uses extensive experience and proven techniques to thoroughly drive out bats and seal entry routes. About BEST Inc.: company name: BEST Inc.; representative: Hirofumi Igarashi, Representative Director and CEO; location: Yokohama, Kanagawa Prefecture; established: 2004; business: life media business; URL: https://best24.co.jp . Contact: BEST Inc. Marketing Department, Email: info@best-24.jp, URL: https://best24.co.jp/ . Related site: BEST365, https://best365.best24.co.jp/ .