Global positioning systems indicate landscape preferences of cattle in the subtropical savannas

Abstract

Large paddocks, a heterogeneous landscape and widely dispersed water points provide challenges for the sustainable grazing management of northern Australian beef properties. Determining grazing animal distribution and relating this to features in the landscape, including artificial water points, can assist in the sustainable management of these environments. This case study describes the distribution and landscape association of cattle for part of a single wet season. Twelve Brahman cows were fitted with global positioning system (GPS) collars for 8 weeks in a 1530 ha paddock that contained a diversity of land-types and a single artificial water point. Grazing preferences were initially limited to a 250-ha cleared area of clay soil sown with Cenchrus ciliaris. Thereafter, animals moved on to less fertile outlying areas of Eucalyptus and Acacia agyrodendron native pasture woodland. Mean convex polygon, the smallest polygon that contained 90% of positional data, increased from 229 ± 37.6 ha to 449 ± 80.3 ha over the first 3 weeks of the study. Animals avoided areas dominated by steep terrain and the preference index (proportion of GPS locations that occurred in a land-type divided by its relative cover) was less than unity for 71% of the paddock area. Although the performance of the GPS units was disappointing, the study verifies that GPS telemetry and satellite imagery can be used to quantify cattle distribution and probable grazing preferences in the extensive, spatially heterogeneous paddocks of northern Australia.