Corn is the heart and soul of Mexico’s agriculture. It accounts for more than 60 percent of the nation’s total agricultural output and 62 percent of its cultivated land. Up to 18 million people – some 17 percent of Mexico’s population – depend on corn production for their livelihood. And bats help them do it.
Mexican free-tailed bats make a major contribution to protecting corn crops from insect damage – a fact that is almost completely unknown to most farmers in Mexico, where bats face a wide array of perils. Accurate information can be a powerful tool in promoting bat conservation.
Graduate student Leonardo J. López-Damián of the National Autonomous University of Mexico, under the direction of Professor Rodrigo Medellín, who heads the Program for Conservation of Mexican Bats (PCMM), is conducting the first systematic study of the diet of Mexican free-tailed bats in Mexico. PCMM and its parent, the conservation group BIOCONCIENCIA, are sponsoring the study, which is also supported in part by a BCI Student Research Scholarship funded by the U.S. Forest Service International Programs.
Among the most damaging pests of Mexico’s corn crops are two insects: corn earworm (also known as cotton bollworm) moths during summertime in northern Mexico, and fall armyworm moths during winter months in the south.
The researchers worked in three caves, each home to about 1 million Mexican free-tailed bats, in northern, central and southern Mexico. They visited each cave once a month for more than a year, capturing bats as they returned from their nightly foraging.
They netted more than 1,500 Mexican free-tailed bats and obtained nearly 900 samples for dietary analysis. Results showed a very diverse diet, but at the north and central caves, Mexican freetails’ diet is dominated by moths from July to September, right after adult flying moths begin to emerge from cornfields in June. In the south, where freetails are found year-round, moth consumption peaks from January to March and again from August to December. This coincides with moth emergences from cornfields in the region.
Bats are clearly taking advantage of this abundant food supply and feeding heavily on moths that wreak so much destruction on Mexico’s most important crop.
BCI members can read the whole story of Mexican free-tailed bats’ role in protecting Mexico’s corn crop in the Winter 2007 issue of BATS magazine.
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