|Behavioural and physiological responses of domestic sheep (Ovis aries) to the presence of humans and dogs
Doctor of Philosophy in Animal Science
Ngaio Jessica Beausoleil
Both humans and dogs are integral in sheep production systems; however, which is more aversive to sheep, or indeed, whether either causes significant stress, has not been shown experimentally. The aim of this thesis was to examine some behavioural and physiological responses of domestic sheep to the presence of humans or dogs. An arena test was used to measure the relative aversion of sheep to the presence of a human or dog, as well as to elucidate differences in the responses of flocks at the University of Western Australia (UWA) which were putatively selected for differences in fearfulness. A Y maze preference test was used to ‘ask’ sheep whether they preferred a human shaking a rattle or a barking dog. In both tests, adrenocortical responses were measured concurrently to support the interpretation of behaviour.
The presence of a human or dog in the arena elicited significantly more avoidance and vigilance behaviour and less exploration than did the presence of a control object. However, the dog elicited significantly more of this fear-related behaviour and significantly larger adrenocortical responses than did the human. Sheep also expressed a clear preference for a human shaking a rattle over a barking dog in the Y maze test and exhibited larger adrenocortical responses to the dog than to the human in the Y maze facility.
The UWA flocks differed in their expression of locomotor and vocal activity; MA sheep were more active/vocal than the other flocks, not only in the presence of the human but also with the box or dog. MA sheep expressed less avoidance and vigilance and more exploration than the other flocks in the presence of the human and exhibited significantly lower plasma cortisol concentrations than LA sheep after exposure to the human (10-min sample). However, there were no inter-flock differences in fear-related behaviour or adrenocortical responses when the flocks were presented with the box or dog. The results do not support the notion that the UWA flocks have been selected for differences in a consistent predisposition to react fearfully.
The adrenocortical responses measured in these studies were only moderate in magnitude and duration, with peak plasma cortisol concentrations 2-3 times higher than pre-treatment values, and all concentrations returning to pre-treatment levels within one hour of the start of treatment. If these observations are confirmed in practical situations, the presence of humans and dogs during routine handling should cause little concern on the basis of animal welfare. However, limiting the presence of dogs in certain situations (e.g. before slaughter) may reduce stress in domestic sheep.
Significant methodological developments in this research include the use of multivariate statistical techniques to analyze arena behaviour, the concurrent measurement of adrenocortical and behavioural responses in the arena and Y maze tests, and the explicit testing of the effects of individual lateral biases on choice behaviour in a Y maze test. Future studies should measure sheep stress responses to the presence of humans and dogs in practical situations.