According to the Ohio Department of Natural Resources, there are 11 species of bats (out of about 1,200 worldwide) found in Ohio. All are insectivores and the most common are the big brown and little brown bats. While bats may have a bad reputation among the general public, they are an important part of our environment and provide humans with many benefits. Unfortunately, bats face many human-caused challenges that threaten their future. Several species of bats are experiencing declining populations due to various factors, but there are opportunities to help turn around this unfortunate trend.
Why should you care about bats?
A colony of insectivorous bats can consume thousands, even hundreds of thousands, of insects over several weeks of feeding. This is beneficial to many people: from the teen at soccer practice who doesn’t want to be bitten by insects, to the local farmer who wants his crops to grow healthy and free of pest invasions. Recent research estimates that the loss of bats in North America could lead to agricultural losses estimated at more than $3.7 billion/year (crop loss & pesticide use) (Boyles et al., 2011). Bats are also important pollinators and seed dispersers. Nectar-feeding bats are critical pollinators for a wide variety of plants of great economic and ecological value. In North America, giant cacti and agave depend on bats for pollination. A few commercial products that depend on bat pollinators include: bananas, peaches, durian (a fruit), cloves, carob (a chocolate substitute) and balsa wood. Fruit-eating bats disperse seeds that help to restore forests, including rainforests that have been cleared. Because they are night foragers, they are not as wary of crossing the clear-cut areas as diurnal birds may be.
The Indiana Bat
The Indiana bat (Myotis sodalis) is a migratory tree-roosting bat that is listed as endangered at the state and federal levels. It spends winters in communal hibernacula, such as an old mine site, and migrates to forested areas in the summer, where individuals live under the bark of trees with peeling bark. These trees can be live trees with loose “peely” bark (like a Shagbark Hickory) or standing dead/dying trees of any species (called a snag) with loose bark or cavities that provide small hiding places. Males will often roost alone or in a small “bachelor colony.” Male Indiana bats have been observed roosting in trees as small as 3 inches dbh (diameter at breast height) (USFWS, 2013). Females, however, roost in maternity colonies that can number in the hundreds. Because of the high numbers, the maternity colonies require a larger tree (typically >9” dbh) that receives sun exposure for at least half of the day (USFWS, 2007). Maternity colonies will use multiple trees in an area and the proportion of bats using a specific tree determines if it is a primary or alternate roost tree. The colony will usually use 10–20 different trees each year, but only 1–3 of these are primary roosts. Proximity to water, such as streams or wetlands, is another important factor these bats will look for when selecting a roost site.
The population decline for this species is related to several main causes: white-nose syndrome (WNS), wind turbines, and summer habitat loss/fragmentation. WNS is caused by a whitish fungus (Geomyces destructans) that appears on the bats muzzle, hence the name. It spreads rapidly in communal hibernacula where individuals live in very close proximity. It is believed that humans brought the disease over from Europe and spread it around the country during caving activities. Stress from the fungus causes the bats to come out of hibernation too early. They do not have enough fat reserves and due to the time of year there is not a substantial food source. Wind turbines pose a different threat. With the push for sustainable energy, large wind farms are being built. While these developments provide many benefits, the wind turbines can harm bats. The force of the spinning blades creates a change in pressure that ruptures capillaries along the edges of their lungs (Baerwald et al., 2008). Researchers are looking into this phenomenon and some believe that bats may be somehow attracted to the turbines. Solutions are being sought to reduce the potential for bat mortality around these installations. A third factor, summer habitat loss and fragmentation, removes or disconnects bats from areas they would use. The removal of trees with sloughing bark or snags effectively reduces the amount of habitat available to bats within their summer range, creating greater competition for the available resources. Tree removal and forest fragmentation also removes corridors that bats use while foraging. Indiana bats have been shown to exhibit site fidelity, returning to the same forested areas year after year, so removing forested areas and corridors can create an issue. Not much is known yet as to how Indiana bats react to the loss of habitat in areas where they have exhibited site fidelity. Additional sources of population decline can be linked to pesticide use and cave alterations.
How can you help?
- Think before cutting. Bats may be living in your dead/dying trees or any live trees with peeling bark. Just because you think it no longer looks nice doesn’t mean it isn’t important. If it poses a safety issue or you really must remove it then try to cut it during the winter when bats are at their hibernacula.
- Install a bat box. Bat boxes provide bats with somewhere to live. This is especially helpful if you must cut trees down or remove bats that may have gotten into your house.
- Remove bats from your house safely. When bats get in your house it is often by mistake. Shutting off the lights and opening your doors and windows may help guide the bat outdoors. If bats are living in your attic the best way is to exclude them so they cannot regain entry. For more information visit Bat Conservation International’s site on Bat Removal.
- Volunteer! MAD Scientist & Associates recently volunteered with the Ohio Department of Natural Resources to complete acoustic surveys. The data collected from this project will be helpful to develop an understanding of the range and preferred habitats types for bat species in Ohio.
- If you need to conduct a bat habitat evaluation as part of a project, please call MAD Scientists & Associates and we can help you understand the regulations, survey your site, and assist you every step along the way.
Baerwald. E.F., G.H. D’Amours, B.J. Klug, R.M.R. Barclay. 26 August 2008. Barotrauma is a significant cause of bat fatalities at wind turbines. Current Biology.
J.G. Boyles, P. Cryan, G. McCracken and T. Kunz. 1 April 2011. Economic importance of bats
in agriculture. Science.
USFWS Ecological Services. January 2007. Indiana Bat – Summer Life History Information for Michigan.
USFWS Great Lakes-Big Rivers Region. April 2007. Indiana Bat Draft Recovery Plan First Revision.
USFWS Midwest Endangered Species Program. April 2013. Revised Range-wide Indiana Bat Summer Survey Guidelines.