Tracking the Movement of Hair Sheep Grazing in Pastures in the Tropics

The objective of this study was to monitor the location of tropically adapted hair sheep while grazing in a pasture. Non-pregnant, non-lactating, multiparous St. Croix White (STX, 5.6 y of age, 43 kg, n = 5) and Dorper x St Croix White (DRPX, 3.8 y of age, 43 kg, n = 5) ewes were equipped with global positioning system (GPS) tracking collars (Telemetry Solutions, CA) programed to record location at 10-min intervals for 5 consecutive d each mo for a yr to monitor their movement in a 0.6 ha pasture. A grid overlay of the pasture was developed using longitude and latitude coordinates from a handheld GPS unit (Montana 650t, Garmin Ltd, Olathe, KS) to divide the pasture into 16 sections. Several of the grids received shade from two trees during various times of the day. GPS data within each day was divided into time periods based on time of day (Nite-AM = 00:00 to 06:00 h, Day-AM 06:05 to 13:00 h, Day-PM 13:05 to 18:00 h and Nite-PM 18:05 to 23:55 h. The GPS coordinates for each ewe within each week of data collection were analyzed between breed and wk using PROC FREG and Chi-squared analysis of SAS to determine frequency of time spent in each pasture grid section. Over the entire year mean THI and solar radiation during the Nite-AM, Day-AM, Day-PM and Nite-PM were 74.8, 79.0, 79.6, 76.1 and 4, 526, 427, 1.8 W/m², respectively. During Nite-AM the majority of STX (67.0 %) and DRPX (65.7 %) ewes were distributed across 4 grids in the center of the pasture (P < 0.0001). In the Day-AM period the majority of STX (64.0 %) and DRPX (54.5 %) ewes were located in three grids to the west of the trees in the shade (P < 0.002). During the Day-PM the DRPX and STX ewes were uniformly distributed across the pasture with no concentration of ewes in any grid section (P > 0.10). During Nite-PM STX and DRPX ewes spent 50.6 and 53.1 % of the time in two central grids, respectively (P < 0.004). Hair sheep spent significant time in certain areas of the pasture during the day, perhaps in order to utilize shade provide by trees.