(The following is excerpted from “Barn Owl–a biological rat trap” in Groundcover No. 24, 1996.) “In Malaysia it has been estimated that it costs oil palm growers US$45 million to control rats. Not only that but they consume US$16.9 million worth of rice each year.” “In the eighties the Palm Oil Research Institute of Malaysia introduced barn owls into an integrated pest management program. The success of the owls became obvious almost overnight…mainly because the birds were given artificial nesting sites. Inadequate nesting areas had discouraged owls from breeding despite the food surplus. In one oil palm estate, the occupancy rate of nesting sites reached 80% during the breeding season.” They recommend placing one nest box every 10 ha. “The Malaysian research has helped dispel the myth that barn owls hunt only in open areas. They found that the birds change their hunting mode to suite the vegetation. Instead of flying over the area scouting for prey the owls perch on palm fronds and wait for rats to pass by. The researchers put up perching posts to encourage this.” The owls eat almost nothing but rodents. A breeding pair of owls with offspring need about 1200 rats per year. To encourage populations of owls and other natural predators (e. g. chameleons and snakes), islands of natural vegetation in fields should be preserved.