Bats eat insects. Many insects are agricultural pests that cause much damage to crops. For example, many caterpillars do extensive damage to crops and forests, caterpillars that turn into the moths that mate and create new caterpillars. Bats are key predators of moths.
In fact, bats are the only major night predator of beetles, moths and other insects known to damage farmer’s crops and productive forests.
But the relationship isn’t always clear. The people studying bats have done a great job in filling in many details, but bat research is not exactly one of the hot areas of the academic world. Unfortunately, what is not known about bats is far greater than what we do know.
However, research has been done in many areas and continues to be done to discover what bats contribute to agriculture. Mexican free-tailed bats are known to eat several species of moths that are agricultural pests in Texas. For example, about 100 million of these bats live in eight counties in south-central Texas. The cotton bollworm moth (also known as the corn earworm moth – it like both crops) is a serious problem there, and these millions of bats consume approximately 4 billion insects every night! That’s a lot of moths gone that can’t reproduce. In 2007, researchers determined that these bats could reduce the number of insecticide applications needed per year, saving farmers $19-34 per acre of cotton in insecticide costs. Plus there is the benefit of using less insecticides in the environment.
Bats have been used effectively in vineyards and almond orchards in California. In these locations, bat houses have been placed around the fields to attract bats. As these houses have become occupied, bats have had an impact on the insects in those vineyards and almond orchards. Some organic farms in Oregon have experimented with attracting bats, too, and farmers have reported good results in reducing insect pest problems.
Bat Conservation International estimates that bats save farmers $23 billion each year in reduced pesticide use and less crop damage.
Most species of bats are generalists and opportunists, feeding on a variety of insects. Do they then reduce mosquito populations? Bats have been reported to feed on mosquitoes in many parts of the country, but most bats seem not to prefer mosquitoes and will eat other insects if they are available. So they while they likely have an impact on mosquitoes, that impact is generally probably not a big one. Research has shown that insects will avoid areas where bats frequent, however, so having bats around will be a benefit.