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Selection during the last decades has split some established dog breeds into morphologically and behaviourally divergent types. These breed splits are interesting models for behaviour genetics since selection has often been for few and well-defined behavioural traits. The aim of this study was to explore behavioural differences between selection lines in golden and Labrador retriever, in both of which a split between a common type (pet and conformation) and a field type (hunting) has occurred. We hypothesized that the behavioural profiles of the types would be similar in both breeds. Pedigree data and results from a standardized behavioural test from 902 goldens (698 common and 204 field) and 1672 Labradors (1023 and 649) were analysed. Principal component analysis revealed six behavioural components: curiosity, play interest, chase proneness, social curiosity, social greeting and threat display. Breed and type affected all components, but interestingly there was an interaction between breed and type for most components. For example, in Labradors the common type had higher curiosity than the field type (F1,1668 = 18.359; P < 0.001), while the opposite was found in goldens (F1,897 = 65.201; P < 0.001). Heritability estimates showed considerable genetic contributions to the behavioural variations in both breeds, but different heritabilities between the types within breeds was also found, suggesting different selection pressures. In conclusion, in spite of similar genetic origin and similar recent selection criteria, types behave differently in the breeds. This suggests that the genetic architecture related to behaviour differs between the breeds.
Differences between and within breeds are shown in Fig. 1 and F and P values of the main factors and the breed × type interaction are shown in Table 3. Firstly, breed had a significant effect on all of the six components, where Labradors showed higher curiosity, play interest and threat display and goldens higher chase proneness, higher social curiosity and higher social greeting. Additionally, type had a significant effect on all components. However, in four of the components, namely curiosity, play interest, social curiosity and social greeting, there was a significant interaction between breed and type. For chase proneness, there was a trend for an interaction between breed and type. Thus, the effect of type on the components differed depending on breed. Within the goldens, field‐bred dogs had higher curiosity (F1,897 = 65.201; P < 0.001), play interest (F1,897 = 46.146; P < 0.001), chase proneness (F1,898 = 17.807; P < 0.001) and social greeting (F1,897 = 9.097; P = 0.003), while there was no difference between the types in social curiosity. Within the Labradors, field‐bred dogs had a higher play interest (F1,1668 = 18.359; P < 0.001) while common‐bred dogs had higher curiosity (F1,1668 = 29.855; P < 0.001), social curiosity (F1,1668 = 28.532; P < 0.001) and social greeting (F1,1668 = 116.955; P < 0.001). Chase proneness did not differ significantly between the types within Labradors.