Manipulating cattle distribution with salt and water in large arid-land pastures: a GPS/GIS assessment.

Several of the problems associated with grazing animals in extensive settings are related to their uneven patterns of use across the landscape. After fencing, water and salt are two of the most frequently used tools for affecting cattle distribution in extensive settings. Cattle are attracted to water in arid regions, but mixed results have been obtained with salt and mineral supplements. The goal of this study was to evaluate the efficacies of salt and water manipulations for affecting cattle distribution in large (>825ha) pastures. This was accomplished by fitting cattle with global positioning system (GPS) collars and monitoring their travels and activities in a three pasture, Latin-square design where water and salt shared a common location and water or salt were moved individually to distant areas. Mean distance of cattle from water (&xmacr;=1.16km) was unaffected by treatments (P=0.79) suggesting that cattle followed movements of water tanks. Distance traveled daily (&xmacr;=5.78km), time devoted to grazing (11.0h per day), time devoted to resting (10.1h per day), and the area (&xmacr;=325ha) of minimum convex polygons were also unaffected by treatment implying that cattle did not compensate for separated water and salting areas with increased travels or disruptions of habitual grazing and resting activities. Centers of activity for cattle shifted further (P=0.02) when water (&xmacr;=1.49km) was moved than when salt (&xmacr;=1.00km) was relocated. Mean distance of cattle from salt increased from 1.03km, when salt and water were together, to 1.73km (P=0.08) when salt and water were separated. This implied that cattle made less effort to remain near salt. Also, when water and salt were separated, cattle were found within 250m of water 354 times and close to salt only 38 times. Movement of drinking water to distant points in pastures was the most effective tool for altering cattle distribution. When cattle and salt were introduced to a new portion of a pasture, cattle used the new area for about 2 days, and then began drifting back toward previously used portions of the pasture. Manipulations of salting stations will not significantly rectify serious livestock distribution problems in extensive arid-land pastures.