May 2008, Volume 6, Issue 5

Bats in the News

Bats & Bugs in the Tropics


Birds have always gotten credit for consuming damaging insects in Tropical forests, but two researchers have now proven that underappreciated bats are at least as important as birds for consuming bugs and reducing their damage to plants, the New York Times reports.

 
Papers by the two scientists, both supported in part by Bat Conservation International, were published in the same issue of Science, the prestigious journal of the American Association for the Advancement of Science. Margareta Kalka, of the Smithsonian Tropical Research Center in Panama, was awarded a BCI Student Research Scholarship funded by the U.S. Forest Service International Programs. Kimberley Williams-Guillen, a postdoctoral researcher at the University of Michigan, received a grant from BCI’s North American Bat Conservation Fund.
 
Kalka and Williams-Guillen demonstrated, the Times said, that bats in the tropics “eat so many bugs that they put a significant damper on the number of bugs crawling on plants. … Bug-eating bats are thus a boon to farmers there, reducing the need for insecticides. The findings also highlight incomplete knowledge about the role bats play in many ecosystems.”
 
Reporter Kenneth Chang wrote that few scientists had ever tried to determine bats’ impact on insect populations in tropical forests, and bats, because they fly at night, were often completely ignored.
 
In previous experiments, scientists would cover some plants with netting or cages to keep insects from being eaten by airborne predators, then return later to count the number of insects on the caged versus uncaged plants. The newspaper said, “Fewer insects crawled on the uncaged plants because, the scientists concluded, birds flying around during the day were eating a lot of them.”
 
Williams-Guillen figured insectivorous bats must play a part in those insect-control findings. So she and her colleagues conducted a similar experiment at an organic coffee plantation in Mexico, “except they compared coffee plants caged only during the day (leaving them open for bats at night), plants caged only at night (keeping the bats out at night, but leaving them open to birds during the day), plants caged all day long (excluding both bats and birds) and plants not caged at all,” Chang reported.
 
They found, he wrote, “ that bats accounted for a large part of the insect consumptions, especially during the wet season in summer, when bats reproduce and mother bats have to eat prodigiously to nurse their offspring. The opposite is true during the winter months when an influx of migrating insect-eating songbirds arrive from the United States and Canada.”
 
Kalka studied bats’ insect-consumption in a natural forest and found that bats out-ate birds during wet months. (She did not repeat the experiment during dry months.) Kalka told the Times she expects that similar results would be found for bats in temperate regions.
 
The New York Times said the findings could “influence the method of farming. The coffee plantation studied by Williams-Guillen grew coffee plants under a canopy of shade trees. Higher yields can be grown by eliminating the shade trees – but fewer species of bats frequent such open plantations, and that could mean fewer bats eating the bugs and a greater need for pesticides.”
 
 

BCI Members can read the scientists own account of their research in the Summer 2008 issue of BATS magazine. To help support BCI’s scholarship or North American Bat Conservation Fund programs, please contact development@batcon.org.

BCI Members can read the scientists own account of their research in the Summer 2008 issue of BATS magazine. To help support BCI’s scholarship or North American Bat Conservation Fund programs, please contact development@batcon.org.

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