Environmental Uncertainty Affects Movement and Space-use in Sheep

Abstract

Animals constantly experience periods of uncertainty due to seasonal changes in food distribution. The changing climate results in more variable weather patterns, which in turn alter environmental conditions, and can result in resource distribution being less predictable in space and time. How animals respond to these uncertain conditions, in particular the changing distribution of food resources, remains largely unclear and is an important question in the field of movement and animal ecology. Here we used an experimental approach to study how Merino sheep (Ovis aries) responded to different levels of environmental uncertainty in a drought-impacted region of the Australian arid zone. Sheep were unfamiliar with the experimental resource distribution at the start and progressively decreased their uncertainty (i.e., increased their environmental knowledge) when discovering an increasing number of foraging patches. We tracked 50 sheep with GPS collars (1 location every 15 sec) and deduced their movement and space use behaviour. When environmental uncertainty decreased, individuals moved more directionally (greater step length, smaller turn angles) and moved greater distances per day. They also had larger daily home ranges but rested in similar areas on consecutive nights (similar displacement, with the exception when five patches were discovered). Our study demonstrates how an arid zone, free-ranging ungulate adjusts its movement and space use behaviour as it gains environmental information in order to forage efficiently during periods of uncertainty. Our study provides important insights into how animals cope with variable environments and different levels of uncertainty.