Striking networks of livestock tracks have been observed in hilly rangelands throughout the world. They have strong spatial heterogeneity at local-scales in micro-topography, vegetation, soil physical properties, and hydrological and bio-geochemical processes. However, we have limited knowledge of the structural characteristics of these networks and their implications to energy efficiency of the foraging livestock. Fifteen sites on hilly rangelands of Loess Plateau were selected for examining the structural characteristics of the goat tracks and their use by goats. The tracks in each site were processed to generate a graph of the network that consisted of “vertices” (points where tracks intersected or turned) and “track segments” (relatively strait track segments linking pairs of vertices). Each track segment was classified as either parallel or conjunctive based on its track angle (the angle between a track segment and the horizontal line on the hillside) relative to that of connecting track(s). The network structural characteristics and the pattern of use by goats were quantified.
Results/Conclusions
Rather than simply composed of long parallel tracks with interspersed short conjunctive tracks, the goat tracks were relative tortuousness with short track segments and the distinction between parallel and conjunctive tracks was not always clear. The characteristics of the goat track network, with low track angles of parallel segments and near highest sustainable track angles of conjunctive segments, facilitate energy-efficient movement of foraging goats. The well-dispersed distribution of the tracks divides the landscape into elongated polygons that allow goats to access most of the non-track areas while foraging along the tracks. The goats preferentially used segments with lower track angles and smaller turn angles. The network structure is likely maintained by goats’ preferential use of the track segments with high efficiency for movement and forage access, while track segments with low efficiency are trampled less and thus reduced overtime. Given the potential positive effects of goat track networks on soil and water conservation as well as forage efficiency, careful assessment of the potential implications of the recent policy to exclude grazing over expansive regions of hilly rangelands of Loess Plateau and explorations of alternative approaches are warranted.