Inferred spatial use by elephants is robust to landscape effects on GPS telemetry

Abstract

Global Positioning System (GPS) telemetry provides data to study spatial utilization patterns of animals. Spatial uncertainty due to poor accuracy and fix rates, however, may detract from inferences based on such data. The exclusion of two-dimensional (2D) locations may improve such inferences, but the prevalence of 2D locations may be a factor of landscape properties. In trials conducted using GPS units stationed at known positions, fix rate decreased significantly with increased canopy cover, but was unaffected by slope. Most (75%) of the locations recorded in closed woodland were 2D locations, suggesting that the exclusion of 2D locations may reduce estimates of the utilization of such habitats. Excluding 2D locations from records obtained for GPS units deployed on free-ranging elephants (Loxodonta africana) increased daily displacement distances, and changed the number of locations per habitat. However, selection ratios and estimates of home range area were not influenced by filtering location data. We concluded that although the exclusion of 2D locations improved the accuracy of locations per se, it resulted in significant data loss. This loss could alter inferences on patterns of spatial utilization.