Bats: Insects for dinner

KAREN ZINCK

Dig in with the Mas­ter Gardeners

When you men­tion bats, many peo­ple have an instant reac­tion and it’s not often a pos­i­tive one. Our cul­ture is rich with bat imagery and every Octo­ber we can immerse our­selves in spine tin­gling spook­i­ness or dark and mys­te­ri­ous fes­tiv­i­ties. Either way, bats play a key role at Hal­loween. And how many of us went camp­ing as kids and tried to scare each other after dark by ruf­fling each other’s hair and say­ing it was a bat? That was always good for a scream! The truth is that bats in North Amer­ica only eat insects, and unless you actu­ally throw one at that weird kid, they never get tan­gled in anyone’s hair. In fact, bats are a pro­foundly impor­tant part of our nat­ural environment.

There are cur­rently 1,116 bat species iden­ti­fied world­wide, with the major­ity of them liv­ing in trop­i­cal regions. Of these, only 44 species live in the U.S. and Canada. They range in size from 0.07 ounces with a wing span of about 4 inches, to more than 2 pounds with a wing span of almost 6 feet. All of these North Amer­i­can bats hiber­nate in the win­ter and give birth only once every spring to a lit­ter of only one or two off­spring. Female bats suckle their young with milk for about four to six weeks.

Bats in North Amer­ica are pol­li­na­tors and vora­cious con­sumers of mos­qui­toes and insect pests. Accord­ing to Boston University’s Kunz Bat Lab, a sin­gle bat will eat up to one half of its body weight in insects in one balmy night. The lab extrap­o­lated this data to the pop­u­la­tion of bats liv­ing in a 100-mile area of New Eng­land. Using the con­ser­v­a­tive num­ber of 50,000 bats they cal­cu­lated that over 13 tons of insects are con­sumed in one sum­mer! That is 13 tons of noc­tur­nal insects, includ­ing many crop and for­est pests. Now try to imag­ine how much pes­ti­cide would be needed to do that job for ourselves.

Here is the bad news. Our bat pop­u­la­tions in North Amer­ica are fac­ing two new and seri­ous threats: White-Nose syn­drome, and the increased devel­op­ment of wind-power facil­i­ties. Both of these threats are described in detail in the April edi­tion of the jour­nal SCIENCE (“Eco­nomic Impor­tance of Bats in Agri­cul­ture” Vol. 332). This arti­cle was sum­ma­rized and dis­cussed in May’s Ohio Coun­try Journal.

White-Nose syn­drome was first detected in New York State in 2006. It is a fun­gal skin infec­tion that attacks while the bats are hiber­nat­ing in caves. It kills 90–100 per­cent of bats in infected colonies over two or three sea­sons. WNS is esti­mated to have killed more than one mil­lion bats in the north­east­ern U.S. to date. Both Ohio and Ken­tucky announced this spring that the dis­ease had arrived, bring­ing the total affected area to 16 states and three Cana­dian Provinces.

This rapidly spread­ing dis­ease is expected to cause bil­lions of dol­lars in losses to North Amer­i­can agri­cul­ture in the com­ing years. Data from the SCIENCE arti­cle was extrap­o­lated to show that the esti­mated losses for Ohio would be expected to range from $740 mil­lion up to approx­i­mately $1.7 bil­lion per year. How­ever, as the OSU Extension/Delaware County points out, most of the data came from Texas and was applied to cot­ton crops. Ohio’s corn and soy­bean crops have not been studied.

The cur­rent data con­sid­ers crop acreage, the num­ber of crop pests eaten by bats, the dam­age to crops that is pre­vented by the bats, and the result­ing need for farm­ers to spend less on pes­ti­cides. Until spe­cific com­bi­na­tions of crop vari­eties and bat species are exam­ined, it is impos­si­ble to deter­mine if any notice­able impact will be felt in Ohio.

As for the prob­lems caused by wind tur­bines, there are cur­rently no continent-wide mon­i­tor­ing pro­grams that track wildlife fatal­i­ties at these sites so the num­bers of migra­tory bats being killed is dif­fi­cult to assess. How­ever, sig­nif­i­cant num­bers of sev­eral bat species are being found dead and atten­tion is now focus­ing on find­ing out why.

Thriv­ing bat pop­u­la­tions are so impor­tant to the Earth’s ecol­ogy that U.S. and inter­na­tional agri­cul­tural agen­cies are now work­ing together to find solu­tions to the most urgent threats. Right now the best we can do as indi­vid­u­als is to appre­ci­ate our bats and prac­tice mind­ful gardening.

Karen Zinck is an OSU Exten­sion Delaware County Mas­ter Gar­dener Volunteer.

Posted by Master Gardener on Jun 4 2011. You can follow any responses to this entry through the RSS Feed. Comments can be made below.