'The Effects of Uncertainty on Movement and Space-use in Sheep'

Abstract

Within the growing field of movement ecology, the way animals respond to uncertainty caused by changing environments is of great interest. Our changing climate and associated diminishing resources could challenge specific animal communities. Food resource locations across the landscape could become less predictable, and animals must adjust their foraging behaviour when responding to these changes. However, how animals react to this uncertainty remains unclear. Here I studied the movement behaviour of Merino sheep situated in a drought-impacted region of arid New South Wales. GPS tracking of 50 individuals recorded individual locations every 15 seconds during daylight hours. Movements within a period where the sheep had gained little environmental information and were more uncertain of the type and distribution of available environmental resources were compared with a subsequent period where resources were relocated. Still, despite this, the animals had gained higher overall knowledge of resource locations throughout the second period. During the period of uncertainty, individuals were found to have slower walking speeds, travelled shorter distances per day and were generally less displaced from their daily starting location. The sheep also had smaller home ranges and more severe turn angles during periods where their knowledge of the environment was limited. This study shows that individuals experiencing higher levels of uncertainty use a 'win-stay' foraging strategy, whereas as more high-value resources are discovered, a 'win-shift' strategy is adopted. This study demonstrates that arid zone, free-ranging ungulates have the capability to quickly adjust their movement strategy to enhance efficiency in changed conditions as they gain environmental information. These findings may facilitate the study of the effects of uncertainty and impacts of environmental changes on foraging strategies in wild ungulate populations.