Bats are nocturnal mammals fundamental to many ecosystems. Their presence is driven by three survival requirements: a reliable food source, accessible water, and secure shelter. Understanding what attracts these creatures is the first step toward promoting coexistence or managing their presence around human habitations. The specific attractants bats seek are linked to their unique biology and needs during the active summer months.
The Allure of Insect Prey
The primary attraction for most North American bats is the abundance of night-flying insects. Over 40 species in the United States are insectivorous, and their foraging behavior is concentrated in areas where prey populations thrive. A single small brown bat can consume approximately 4 to 8 grams of insects nightly, equating to a significant ecological service for pest control.
Bats are drawn to locations that concentrate their insect food source, such as agricultural fields or areas near standing water. Fast-flying species, like the big brown bat, target larger prey like beetles, while others specialize in small insects like mosquitoes and gnats. This hunt is guided by echolocation, allowing them to locate and capture insects on the wing, often using their tail or wing membranes to trap the prey before eating it.
Artificial outdoor lighting inadvertently creates feeding grounds for bats. Lights that emit short-wavelength blue or ultraviolet light attract swarms of moths and other insects. Light-tolerant bat species, such as some pipistrelles, exploit these concentrated insect buffets for easy hunting. However, many slower-flying bat species avoid lit areas completely, sticking to dark corridors to avoid predators.
Habitat and Roosting Preferences
Bats seek shelter, or roosts, that provide specific microclimates to conserve energy and successfully rear their young. The selection of a roost is primarily determined by the need for thermal stability, which varies depending on the season and reproductive status.
Maternity colonies, composed of female bats and their pups, require warm, stable conditions, ideally with temperatures ranging from 80°F to 100°F (30°C to 38°C). These higher temperatures allow the young to grow rapidly while the mothers are out foraging. Bats often choose roosts with significant solar exposure, such as under the eaves of buildings, in hot attics, or behind loose tree bark.
Conversely, during the winter hibernation period, bats seek cool, stable environments to lower their body temperature and survive on stored fat reserves. Hibernation sites, typically caves or abandoned mines, maintain temperatures close to freezing, generally between 32°F and 50°F (0°C and 10°C). Roosting structures must also offer protection from predators and wind, often utilizing narrow crevices or small gaps that are inaccessible to larger animals.
Attraction to Water Sources
Water is a requirement for bats, not only for hydration but also because it is a source of food. They tend to drink while flying, rapidly skimming the surface of open water bodies with their mouths agape. This dipping and sipping technique necessitates a clear, smooth surface, making still ponds, lakes, or even swimming pools highly attractive.
Female bats require significantly more water when they are lactating, sometimes visiting water sources up to 13 times more often than non-breeding females. Additionally, water bodies are natural breeding grounds for aquatic insects like caddisflies and midges, which emerge at night in dense swarms. The presence of water offers a dual benefit: a hydration source and a rich hunting ground for insect prey.
Using Attraction Knowledge for Coexistence
The knowledge of bat attractants can be applied to encourage their presence for natural pest control or to deter them from unwanted areas. To safely attract bats, install a multi-chamber bat house, which provides the necessary thermal stability for a maternity colony.
The bat house should be mounted on a building or a pole, at least 12 feet high, and oriented to face south or southeast to receive a minimum of six hours of direct sunlight each day. In colder climates, painting the bat house a dark color helps it absorb heat and maintain the internal temperature bats prefer. Gardeners can also plant a “moon garden” featuring night-blooming, pale, and fragrant flowers like Evening Primrose or Nicotiana. These plants lure the moths and beetles that bats feed on, effectively establishing a local food source.
To deter bats from roosting inside a structure, the first step is to identify and seal all openings larger than a quarter-inch, as bats can squeeze through very small gaps. For the main entry point, a humane one-way exclusion device, such as a plastic tube or netting, should be installed. This device is angled downward to allow bats to exit at dusk but prevents them from re-entering at dawn, and it must be left in place for five to seven nights. Deterrents like mothballs or ultrasonic devices are ineffective and potentially harmful, and should not be used.