Preliminary indications that Merino sheep graze different areas on cooler days in the Southern Rangelands of Western Australia

Abstract

High ambient temperature can decrease weight gain in livestock, but domestic livestock in extensive grazing systems may have some capacity to adjust their behaviour to reduce the impact of periods of high temperature. We hypothesised that sheep grazing in the semiarid Southern Rangelands of Western Australia would reduce distance travelled on days with high mean daily temperature. Eight Merino ewes were fitted with GPS collars for 3 weeks in a 5575-ha paddock on Carlaminda station (28°20′S, 116°41′E). Mean daily temperature was used to separate the 18 days of the study into three temperature classes, cool (≤23.2°C), warm (23.3 to 25.9°C) and hot (≥26.0°C). Sheep travelled more quickly (P < 0.05) and further from water on cool days, compared with warm and hot days (3.74 v. 2.93 and 2.73 km from water, respectively; P < 0.001). On cool days, sheep spent most of their time grazing in the western area of the paddock. This area was rarely visited on warm or hot days. Mapping livestock distribution may assist in strategic relocation of existing water points and/or justify the development of additional watering points. However, our results suggest that sheep adjust their behaviour during hot weather, which may be a strategy to conserve energy, manage higher water requirements and/or reduce thermal load. Although grazing range decreases with higher temperatures, overall utilisation of a paddock may not be severely affected unless cooler days were too infrequent to facilitate regular access to these areas.