Long-term stress in dogs is related to the human–dog relationship and personality traits
Previously, we found that dogs belonging to the herding breed group, selected for human cooperation, synchronise their long-term stress levels with their owners. The aim of the current study was to investigate features that could influence long-term stress levels in ancient dog breeds, genetically closer to wolves, and dogs specifically selected to work independently of their owner. Twenty-four ancient breed dogs and 18 solitary hunting dogs were recruited and hair samples were obtained from both dogs and owners from which hair cortisol concentration (HCC) was analysed. Additionally, the owners completed lifestyle surveys, the Monash Dog Owner Relationship Scale (MDORS) on human–dog relationship, and both dog and owner personality questionnaires (Dog Personality questionnaire and Big Five Inventory survey). The results from the MDORS indicate that the subscale Perceived cost correlated to the dog HCC of tested breed groups: solitary hunting breeds (χ2 = 4.95, P = 0.026, β = 0.055), ancient breeds (χ2 = 2.74, P = 0.098, β = 0.027), and herding dogs included from a previous study (χ2 = 6.82, P = 0.009, β = − 0.061). The HCC of the solitary hunting dogs was also related to the owner personality traits Agreeableness (χ2 = 12.30, P < 0.001, β = − 0.060) and Openness (χ2 = 9.56, P = 0.002, β = 0.048) suggesting a more substantial influence of the owner on the solitary hunting dog’s HCC compared to the ancient breeds. No effect of owner HCC on dog HCC was found in either ancient or in solitary hunting breeds. Hence, the long-term stress synchronisation is likely to be a trait in breeds selected for human cooperation. In conclusion, dog HCC is often related to the owners’ personality, but is primarily influenced by the owner-dog relationship.
In a previous study we found that dogs mirror the long-term stress levels of their owners1. The HCC of the dog was shown to synchronise with the HCC of the owner and was in addition more associated to the owner’s personality compared to its own. Emotional contagion has earlier been shown through both short-term physiological, endocrine, and behavioural responses between dogs and humans2,3,4 and could be a result of the domestication of the dog and sharing everyday life. It might, however, also be affected by the recent breed selection and the working task of the breed. Both border collies and Shetland sheepdogs revealed a strong long-term stress synchronisation with their owners1. However, both belong to the herding breed group, specifically selected to cooperate with humans, and this might have contributed to the stress synchronisation with the owner. Recent selection of breeds, and even breed lines within breeds5, has been shown to affect the behaviour of dogs6, and this might also have an effect on the interspecies emotional contagion. In contrast to herding dogs, the ancient breeds are thought to be closer genetically to wolves7 and have not been selected specifically for human cooperation. Also, there are those breeds that are selected for hunting independently, visually separated from the owner, and that have been shown to differ in both their attention as well as behaviour towards humans8,9. During hunting seasons in Sweden, there is a tradition of releasing hunting dogs into the forest to let them work on their own. The dog will search the terrain, find targeted animals and drive them forward or, alternatively, make them stationary and gain the hunter’s attention through barking. Hence, these dogs are not specifically bred to cooperate with humans but instead bred for their natural hunting skills. In a recent study10 the degree of selection of coopertiveness with humans was shown to affect stress-related behaviours during owner separation. Therefore, we aimed in this study to assess long-term stress levels in hair samples from dogs and their owners, from both solitary hunting dogs as well as ancient dog breeds, and compare the results to our previous study on herding dogs1.
Hair cortisol concentrations (HCC) have repeatedly been shown to be a valuable long-term measurement in various mammals and humans11,12 since the cortisol is incorporated as the hair grows. However, HCC can also be affected by e.g. physical activity13 which might differ between the e.g. solitary hunting breeds and other breed groups. Therefore, we continuously also monitored the dogs activity levels during one week using remote cloud-based activity collar. Since our previous study1 found effects of owner personality traits on the dogs’ HCC, personality surveys were also completed.
Interestingly, human–dog interactions and aspects of the human–dog relationship, including owners’ perceptions of the costs of dog ownership, have previously been shown to be associated with alterations in plasma oxytocin concentrations14. In the current study, we are interested in whether there is also an effect of relationship features on long-term stress levels, as measured from cortisol incorporated in hair. Therefore, the owners of ancient dog breeds and solitary hunting dog breeds included in this study, in addition to the owners of herding breeds of the previous study1, were asked to complete the validated Monash Dog Owner Relationship Scale (MDORS)15.