Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Barn owls for rat control on oil palm plantations - do they work?

Abstract

Although rodenticides have been used successfully for many years to control rats in oil palm plantations, there has been interest recently in biological control using barn owls. The complexity of the predator-prey system and logistical difficulties have made the relationship between owl/rat numbers and subsequent crop damage difficult to study using normal techniques. Two alternative techniques were therefore studied: computer modelling and practical field observation. The computer modelling suggested that the moderation of rodent populations by owls will only be achieved under a narrow set of starting criteria, namely relatively low rodent numbers and high owl numbers; when rats are numerous, owls are unable to reduce their populations without some external aid, such as the use of rodenticides. The evidence from field observations was conflicting. On at least one plantation, owls successfully controlled rats and presumably maintained a viable predator population. On several other estates, as predicted by the computer model, barn owls were not having a measurable impact on the high and damaging population of rats.