How to Build a Bat House
Bats are fascinating animals that play vital roles in the ecosystems in which they live.
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One role that has huge benefits for our species is that of primary consumers of insects, including mosquitos. An individual bat can consume hundreds of mosquitoes in an hour. Unfortunately, these small flying mammals are in jeopardy for many reasons. Loss of habitat is one threat faced by bats. The use of pesticides and other chemicals along with nursing colonies being exterminated in houses and other buildings are two more serious threats to the health of bat populations. Wind turbines also kill numerous bats.
Another threat to bats, this fungal disease has resulted in the deaths of millions of bats in eastern North America in the last decade. The fungus, which is from Eurasia and was accidentally brought to North America by humans, can survive on people’s boots, clothing and equipment.
The fungus can grow on the muzzles and wings of an infected bat during hibernation. It causes damage to the affected areas. It also results in bats behaving abnormally, including waking more often during hibernation, which uses up vital fat reserves. Some hibernating bat colonies with the fungus result in 100% of the bats dying.
Aside from keeping your property in a relatively natural state, avoiding the use of pesticides and other harmful chemicals and keeping your house (and other structures) in good repair (bats can access openings as small as 1cm in diameter), you can assist bats by building a home or two for them. About 30 years ago, I was given instructions on how to make a bat house. Not being as talented at building things as my wife Lynn, I gave the plans to her. Lynn constructed a beautiful bat house that has been home to at least one bat every year since. The bat house is occupied from spring until fall. Lynn has made two more bat boxes – one with the help of our children. Here are the instructions for the bat home we provide for our bat neighbors in exchange for some natural bug control!
Note: Dimensions are approximate, as sheeting pine is dressed on one side and dimensions are slightly smaller.
Note: We don’t usually use any finish or paint on the exterior, as natural pine will weather dark grey to absorb heat. The inside is also untreated. The exterior of our first bat house was stained to match the house exterior it is mounted on.
Bat houses can be mounted on buildings or poles and should be at least four metres off the ground – preferably higher. Locating the houses in trees isn’t ideal, as this makes the bats more vulnerable to predators. Bat houses located reasonably close to a water source, such as a stream, pond or lake, have a better chance of attracting bats. Bat houses should be located where they receive lots of direct sunlight, and the area around the house should be clear so that the bats can easily enter and exit the house. Do not locate a bat house near bright lights.
While I haven’t seen any of our lodgers up close, the ones that have recently resided in the first bat house Lynn made could be the original tenants, as bats can live for more than 30 years. With serious threats facing bats, I breathe a sigh of relief each spring when it is confirmed that our lodger, or lodgers, have returned to their home for another year.
You can get more information on bats and how you can help them, including building and installing bat houses, at the Bat Conservation International website at the links below.
Text by N. Glenn Perrett
Photographs by Lynn and Glenn Perrett
N. Glenn Perrett and his family live in Mulmur, Ontario, on a property that includes a diversity of animals – including bats. His book on the national parks of southern Ontario was published by Fitzhenry & Whiteside in summer 2019.