A bat house is a manufactured shelter designed to provide a safe, warm roosting site for bats, which have seen a decline in natural habitats. These structures are typically wooden boxes mounted high off the ground, simulating the crevices bats seek out for raising their young and resting during the day. By offering a dedicated space for these nocturnal insectivores, homeowners can participate directly in local wildlife conservation efforts. This guide addresses the factors a property owner should consider before adding one of these unique homes to their yard.
The Ecological Case for Bat Houses
Providing a roosting space for bats offers tangible, natural benefits for your immediate environment. Bats are voracious insect consumers, with some species capable of eating thousands of insects, including mosquitoes and agricultural pests, in a single night. This natural predation helps to control local insect populations without the need for chemical pesticides, promoting a healthier ecosystem and garden. Attracting bats contributes significantly to broader conservation efforts, as many species face threats from habitat loss and diseases like White-Nose Syndrome. Installing a bat house offers these animals a stable, protected location to form maternity colonies and safely raise their pups.
Proper Placement for Attracting Bats
Mounting and Orientation
The location of the bat house is the most important factor determining whether bats will choose to inhabit it. Bat houses require significant solar exposure to maintain the high internal temperatures necessary for maternity colonies to thrive. They should receive at least six to eight hours of direct sunlight per day, making a south or southeast-facing orientation the most effective.
Height and Flight Path
The house must be mounted high off the ground, with a minimum height of 12 feet, though placement between 15 and 20 feet is often more successful. Mount the house on a pole or the side of a building, rather than a tree, as trees offer predators easier access and can shade the house. The area beneath the house should be clear of obstructions for at least 20 feet, allowing the bats a clear flight path. Bats prefer to roost within a quarter-mile of a permanent water source.
Essential Design Features for Successful Bat Houses
Interior Specifications
Successful bat houses are built with specific design parameters to mimic natural crevices and ensure proper thermal regulation. The house should feature multiple roosting chambers, separated by partitions spaced precisely three-quarters to one inch apart, which helps to maintain a stable temperature gradient. These chambers should be at least 20 inches tall and 14 inches wide to accommodate a maternity colony.
Materials and Grip
The interior surfaces of the chambers, including the landing area below the entrance slot, must be roughened to provide bats a secure grip. This is often achieved by scoring horizontal grooves into the wood or lining the surfaces with durable, non-fraying plastic mesh. Rough, untreated exterior-grade wood, such as cedar or exterior plywood, should be used for construction, as pressure-treated wood can be toxic. Darker exterior colors, like black or dark brown, are preferred in cooler climates to maximize heat absorption.
Managing Health and Safety Concerns
Concerns about bats and human health are natural, but the risks associated with a properly installed bat house are minimal. Rabies is the most commonly cited concern, but less than one percent of bats carry the virus, and they generally avoid human contact. Property owners should never handle a bat directly; any bat found on the ground or acting erratically should be reported to local animal control or health officials for testing.
Guano and Histoplasmosis
Another consideration is the accumulation of guano, or bat droppings, beneath the roost. While guano is an excellent, natural fertilizer, large concentrations can pose a risk of histoplasmosis, a respiratory disease caused by inhaling fungal spores found in aged, dry guano. To minimize this risk, guano should be collected regularly or allowed to fall onto a surface that is not frequently disturbed. The potential for noise is negligible, as bats are quiet and their emergence at dusk is often the only sign of their presence.