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Make Your Garden Batty
by Erika Jensen - August 2013

Red bat roosting in foliage.

Imagine that you’ve got a friend in your garden, a beneficent creature with near-magical powers who works all night long while you sleep, kindly removing mosquitoes, as well as many of the pest insects that affect your flowers and vegetables. It sounds too good to be true, yet bats really do all this. To learn about bats, I talked to Jennifer Redell, a scientist with the Wisconsin Bat Monitoring Program, a project of the Wisconsin Department of Natural Resources.

Benefits to Gardeners

“Bats are an important form of pest control, since they are the primary predator of night-flying insects,” Redell explained. Although species in other parts of the world may feed on nectar or fruit (only three South American species actually drink blood), all of the species we have in the Upper Midwest are insectivores. They consume the real bloodsuckers in our part of the world – mosquitoes.

Some of the insects they eat are common pests in the garden. For example, the little brown bat eats many species of wasps, moths, leafhoppers and flies and can consume 4-8 grams of insects each night. It’s been estimated that bats save farmers in the United States $12 to $173 an acre through their removal services. They undoubtedly assist gardeners as well.

All About Bats

The Upper Midwest is home to many species of bats, including the little brown bat, big brown bat, northern long-eared bat, eastern pipistrelle, Indiana bat, silver-haired bat, eastern red bat and hoary bat. All use echolocation to capture their prey, although the sounds they make (clicks and buzzes) are outside the range of human hearing.

Bats are long-lived for their size – they can live 25 to 30 years, or longer. Like humans, bats are mammals and most give birth to only one baby at a time, called a pup. The mother nurses the young, and after about four to six weeks, it is able to fly on its own.

Bats can be split into two groups: cave bats and tree bats. Cave bats hibernate in caves during the winter, while tree bats migrate south. They often return to the same bat house year after year, and the same hibernation area (called a hibernaculum) each winter.

Little brown bats using a bat house.


Bats are the primary predator of night-flying insects and can consume 4-8 grams of insects each night. 1

What Can Gardeners Do to Help Bats?

“Put up a bat house,” Redell said. “Many people are aware that the multi-chambered houses can hold as many as 300 bats. The houses serve as maternity colonies from late May through early June.”

Baby bats like it hot – around 100 F – and actually develop better in warmer temperatures. Site your bat house in full sun, facing south. The bat houses should also be on a post 8-10 feet off the ground.

Bat houses, such as these multi-chambered houses, can hold up to 300 bats. Mounting two houses back-to-back helps provide a variety of temperatures for bats to choose from.


White-Nose Syndrome   

White-nose syndrome is a new disease first recorded in 2006 in New York State. Since then, it has spread to 19 other states. In February, the Illinois Department of Natural Resources confirmed the presence of white-nose in four counties. Visit whitenosesyndrome.org/news/wns-confirmed-illinois-bats-february-28-2013 for more information.

The disease is caused by a fungus, a white powdery substance that grows on the bat’s nose and skin. The fungus causes the bats to wake up when they should be hibernating, using up precious energy reserves. Only those species that hibernate in caves, not those that migrate, seem to be affected.

The disease is devastating with 90-100 percent mortality in every infected hibernaculum. An estimated 5.7 million bats have already been killed, and some species may become extinct.

But it’s not enough to just put up a bat house. Ideally you should also provide a habitat where bats can find food. Small brush piles, riparian corridors, hedgerows and night-blooming flowers are all habitat features that might attract bats. Different species of bats prefer different habitats – from open fields to forest edges. All of them like to have a source of water within 1 mile, preferably a larger pond (8-by-8 feet) or other body of water.

Gardening organically can also make a difference. When bats are exposed to pesticides through the food they eat, toxins can build up in their fat deposits and cause problems, such as birth defects and death. Like humans, bats are near the top of the food chain and have to watch what they eat.



1 Photo by Matt Reinbold. All other photos courtesy of Wisconsin Department of Natural Resources Bat Program.


Erika Jensen gardens in a bat paradise, midway between the Neda mine and the Horicon National Wildlife refuge in Wisconsin.


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Jim Vincent - 08/26/2013

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Christopher (Louisiana - Zone 8a) - 08/27/2013

Interesting article! I may have to put up a bat house in my yard.
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Jim Vincent - 08/27/2013

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