The spatial dimension of pastoral herding: A case study from the northern Negev

Abstract

Sustainable management of heterogeneous grazing systems requires better understanding of the spatial dimension of grazing ecology. We deployed animal-borne GPS devices to map the daily foraging excursions of a shepherded flock of 200 goats under traditional Bedouin management, on a study site in the semiarid region of the northern Negev, Israel. A total of 88 daily foraging excursions were mapped during the herbaceous growing seasons of 2002 and 2003, and the spatial dimension was analyzed with GIS tools. A typical foraging excursion lasted 5.5 h, during which the flock moved across the landscape at an average speed of 0.3 m/s (1.1 km/h) and traveled 5.4 km. The foraging route was highly elongated in shape and reached a distance of 1.5 km from the night corral. Flock movement speed was affected significantly by distance from the night corral, being greatest at shortest and longest distances. Speed decreased with increasing slope angle and differed between aspects. The frequency of flock presence across the study site deviated significantly from random with respect to aspect but not to slope angle and distance from the corral. The effect of aspect changed slightly between the study years. The product of daily distance traveled and flock path width yielded a rate of area coverage of 0.122 km2 per day. The average amount of herbage dry matter removed on any one pass of the flock is therefore in the order of just a few grams per square meter. The use of the area available to the flock was highly non-uniform, which suggests that better planning of grazing management could mitigate negative effects of grazing.