Bats Are Better Than Pesticides

Bats don't need pesticides or electricity to kill mosquitoes – they only need a nice place to live.

by J. Cates

Bela Lugosi gave them a bad rep. But bats are good pals. They're a natural, all-purpose insecticide, and incredibly efficient at their job. One of the little critters can eat 500 mosquitos in an hour, and thousands in a single night, and they'll help you clear the air around your home with no chemicals and no electric zappers.

But sometimes they have to be encouraged to move into the neighbourhood, and a bat-house will provide them with appropriate living quarters. Bats aren't as plentiful as they used to be. In some areas, pesticides have killed off their food supply; in other areas, destruction of wetlands has also decreased the number of insects available for food. Fortunately, with bats in residence nearby, there won't be much need for pesticides.

(Pesticides may over several years even increase insect populations. If pesticides kill off large numbers of insects, the bats lose their food source and die out. Then, when the insect populations climb again, there aren't enough bats to control them.)

Bat-houses are not difficult to build, but it's also possible to buy them in kit form or pre-assembled. A bat-house should be at least two feet tall and 14 inches wide, with a small landing area below the entrance. They can contain several roosting chambers; the partitions between them should be about an inch apart. The wood used for partitions and landing areas should be roughened or covered with small-mesh plastic screening, and the exterior should be painted, a dark colour in cooler climates and lighter colours in hot climates. There may also be vents on the sides and front of bat-houses, depending, as with the paint colour, on the average summer temperatures in your area. Depending on the size, one house can accommodate 30-100 bats, and two bat-houses can be mounted back-to back.

A combination of exterior plywood and cedar has proven to be good construction material, and bats will move into a bat-house mounted on a pole or house (except a house with metal siding) more readily than one mounted on a tree. They like to roost within about a quarter-mile of a lake, river, or stream, in areas with diverse habitat, especially where there is a mixture of natural and agricultural growth. They should be in a location where there will several hours of daily exposure to the sun.

If wasps move into the bat-house before the bats do, they should be removed in late winter or early spring. A bat-house with an open bottom will reduce the chances of either predators or an excess of bat guano becoming a problem.

There are those who may believe the bad press bats have received over the years, but most of it is untrue. The only vampire bats live in South America, and prefer cows to people for their blood du jour. They're clean, and seldom have rabies (of course, other animals living in the wild can also be rabid). And bats won't fly into your hair and get caught. Getting caught in hair is just something bats prefer not to do.

Bats use echolocation to find their food (and stay out of hair), sending out a beep and waiting to hear the echos from the bugs. They can eat as much as half their own weight in a night, using both wings and tail to round up flying insects. And although they're nocturnal, it's possible to see them in action as they fly silhouetted against the evening sky. They always come out just before dark-at the same bat-time, same bat-channel-to begin feeding.

Instructions, including diagrams, for building a proper bat-house are available from several publications and websites.


[From WS August/September 1998]

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