Apple growers in Israel appear to have unwittingly enlisted the help of super-powered nighttime avengers in their battle against pests. Insectivorous bats, which are an effective alternative to chemical insecticides, defend the apple orchards not out of a sense of justice, but mostly because they offer a more bountiful bug buffet than do natural forests, a recently published study shows.
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The study – published by the Israel Society of Ecology & Environmental Sciences Hebrew-language "Ecology & Environment: Journal for Science and Environmental Policy" – was conducted by researchers from Tel Hai Academic College, the Society for the Protection of Nature in Israel’s Mammal Center and the Migal Galilee Research Institute.
To determine which bat species live in the orchards, the researchers set up detectors to record the sounds produced by the bats and then compared them with a library of sounds made by the various species that live in Israel. (Israel has more than 30 species of bats, many more than much larger European countries.) In this way, the researchers were able to capture the sounds of more than 3,500 flights and identify 14 to 16 varieties of bats.
The clear conclusion was that there is a much greater variety of bat species in the orchards than in Israel's natural forests. Eran Levin, one of the researchers from the Mammal Center, said the bats prefer the orchards because there are more insects for them to eat there.
Moths in the orchards are also easy prey for the bats thanks to a method the apple growers use to control their numbers. The growers hang plastic strings in the trees that release pheromones to attract male moths and distract them from finding and mating with females. The distraction also makes them easy for bats to gobble up.
The overall insect population in the orchards has increased as the use of chemical pesticides in the Galilee region has decreased, resulting in more work and more food for the bats. “This preliminary study emphasizes the importance of apple orchards in preserving the biological diversity of insectivorous bats,” the researchers note. “These findings should be taken into account when managing orchards – for example, when considering the use of pesticides or before covering the orchards with nets, a procedure that has become widespread in recent years.”