Could Bat Boxes be the New Bird Houses?
By Sid Greenslate
If you think birds are boring, and bees have made you blue, then bats may be your new best beau for a biological backyard habitat. Since Seattle has been battling a case of salmonella from bird feeders, it may be a fortuitous time to expand your horizons and invite some little brown bats into your life. Bird houses, Mason bee houses, and even squirrel picnic tables have all had their moment in the spotlight as the backyard habitat en vogue. However, one addition to the animal architecture market that deserves more consideration is the bat house, or bat box.
Bats are widespread throughout North America, and are one of the most diverse mammal groups in the world. In nature they prefer to live in rock crevices, dead standing trees (called snags) and caves. However, some bats species have become opportunistic urban dwellers, finding places to roost in bridges, attics and garages. Our native Washington bats are all insectivores and aim to live close to insect-rich locations, typically near still water that breeds mosquitoes, caddisflies and moths. Considering how many houses are built right up to the water’s edge in Seattle, there are likely many places where a bat house would be considered prime real estate. The bats will also pay their rent in the sheer volume of mosquitoes and other insects they eat. In spring, when pregnant bats are feeding, a single female can eat up to half her weight in bugs in a single evening.
A search for “bat box” on Amazon reveals dozens of styles and price points with the majority ranging from twenty to forty dollars. But not all bat boxes are created equal - a recent study conducted in Australia found that bat boxes made from cheap materials like plywood got hotter during the day and colder at night compared to other types of roosting spaces, like the cavities of tree trunks. When home shopping, a bat’s top priority is thermal regulation, to help control their metabolic rate while sleeping during the day and provide adequate heat through the night. Dramatic temperature variation in roosts used by pregnant bats can cause weakness in newborn bat pups, and a colony may abandon a roost if it causes temperature stress.
What makes a bat house successful? In order to retain enough heat, the world’s dominant bat expert, Merlin Tuttle, suggests at least half-inch thick plywood be used for the main structure of the house. They can also be painted in dark colors to better absorb sunlight, and should be placed somewhere that gets direct sunlight for at least half the day. Depending on the overall size of the box, the inside is one or two narrow chambers, ideally three-quarters of an inch wide, where bats can snuggle themselves in during the day. To help them keep their grip inside the box, grooves or wire mesh should be installed to give them footholds and traction.
If well designed and placed appropriately, a bat house can become a beautiful and unique addition to a home or backyard, as well as an opportunity for free entertainment on summer evenings when the bats come out to forage. It can also serve as an important statement of support for an animal that has long been misunderstood and undeservedly feared in the United States.
Cover Photo by Kelly Sikkema on Unsplash. Article Photo by Sid Greenslate.