Genetisk och etologisk analys av vallningsbeteende hos border collie

Abstract: The ability of a dog to perform some kind of practical work, for example hunting or herding, depends among other things on its behavioural characteristics. In animal breeding it is not always easy though to select for behavioural traits. It may, for example, be difficult to identify traits that are not only heritable but also of importance for the dogs' ability to perform the practical work of interest. Moreover, it is often difficult to accomplish accurate measurements of behavioural traits. When selecting dogs for breeding, it is usually preferable to evaluate them using an objective and standardized bahavioural test, rather than results from field trials. The Swedish Herding Dogs Club (Svenska Vallhundsklubben, SVaK) use a standardized method, here named AHC, to assess the herding characteristics of dogs, especially border collies. The dogs' typical behaviour, mainly towards sheep, is described using predefined scales. The AHC has existed in two versions, and since the start in 1989 almost 2700 border collies have participated. In this study close to 2700 AHC-results, together with pedigree information, have been used to estimate breeding values for the participating dogs and heritabilities for the traits assessed in the AHC. Using factor analysis the herding traits of the AHC have been combined to broader traits. Breeding values, heritabilities and genetic correlations were estimated for the broader traits. Heritabilities for the 17 traits of the earlier version of the AHC were estimated to between 0.14 and 0.50. All traits but two showed medium to high heritabilities. Standard errors varied between 0.043 and 0.060. Heritabilities of the 19 traits of the later version of the AHC varied between 0.03 and 0.41 with standard errors 0.041-0.074. All traits but one showed low to medium heritabilities. There are several possible explanations for the lower heritabilities in the later version. For example the scales, i.e. the way the traits are measured, might have a less appropriate construction. Also, the traits seem to be less well defined, maybe resulting in confusion among judges. In the earlier version of the AHC there were 12 traits describing the dogs' behaviour towards the herd. The factor analyses suggest that these can be explained by four overall traits, which I have chosen to call Authority/Concentration, Distance to herd, Speed and Tendency to bite. The heritabilities for each overall trait are higher than for any of that trait's component traits (with the exception of Tendency to bite, which corresponds to a single original trait). The higher heritabilities are probably due to rather high genetic correlations between the component (original) traits. A secondary factor analysis revealed that nine of the twelve traits could be explained by one broad trait, which I have called Herding characteristic. The heritability for Herding characteristic was estimated to 0.55 with standard error 0.055. To try to explain the outcome of the factor analyses, I have discussed two different models. According to the first model, equivalences to the overall herding traits can be found in the wolf's hunting sequence. The second model explains the overall traits as being expressions for the personality traits Extraversion and Neuroticism. The first model does not exclude the second or vice versa. But even though there is no question that a herding border collie uses hunting behaviours, it is also reasonable to assume that the purpose of these behaviours differs between the hunting wolf and the herding border collie. Therefore I find it easier to understand herding behaviour by applying a personality perspective. When compared to other studies where estimates of heritability of different hunting or herding traits in dogs have been made, the results in the present study show very high heritabilities, especially for the earlier version of the AHC. For several of the traits it is even possible to select animals for breeding using only the phenotypic records. The overall traits are all possible to select for in this way. In other words, there are several possibilities to accomplish effective selection for most of the traits in the earlier version of the AHC.