Exclosure plots as a mechanism for quantifying damage to crops by primates

Abstract

Human-wildlife conflict is a major issue for conservation biologists in the twenty-first century. Crop-damage by wild animals is one element of this conflict, often causing local farmers considerable economic loss and frustration, and undermining local conservation efforts. Formulation of suitable management strategies necessitates accurate measures of crop-damage to allow prioritisation of management efforts and decisions. There is a relative paucity of information from subsistence agricultural settings in Asia. This study represents the first attempt to measure systematically the impact of damage by monkeys to sweet potato crop yields using exclosure plots (3 × 3 m) on Sulawesi, Indonesia. The Buton macaque, Macaca ochreata brunnescens, was responsible for less crop-damage than wild pigs, both in terms of the number of tubers (primates: 35%, pigs: 65%) and total harvested weight (primates: 13%, pigs: 85%). This study also highlights some methodological limitations of exclosure studies and reveals that the exclosures themselves affect crop yields, reducing them by up to 50%. This suggests that estimates of damage should actually be slightly greater; caution should therefore be exercised in the use of such techniques.