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Dog behaviour: Intricate picture of genetics, epigenetics, and human-dog relations
Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dogs, Canis familiaris, share the lives of humans all over the world. That dogs, and the behavior of dogs, are of interest to many is therefore no surprise. In this thesis, the main aim has been to identify factors that affect dogs’ behaviours.

The dog, Canis familiaris, is our first domesticated animal. Since domestication, various types of dogs have developed through adaptation to an environment shared with humans and through our selective breeding, resulting in a unique variation in morphology and behaviour. Although there is an individual variation in the behaviour of dogs, there is also a difference between breeds. Moreover, selection during the last decades has split some breeds into divergent types. Labrador and golden retrievers are divided into a common type, for show and companionship, and a field type, for hunting. By comparing the breed types, we can study the effects of recent selection. In Paper I, we investigate differences in general behavioural traits between Labrador and golden retriever and between common and field type within the two breeds by using results from the standardized behaviour test Dog Mentality Assessment. There were differences between breeds and types for all behavioural traits. However, there was also an interaction between breed and type. Thus, a common/field-type Labrador does not behave like a common/field-type golden retriever. Even though they have been selected for similar traits, the selection has affected the general behavioural traits differently in the two breeds.

In paper II, we were interested in dogs’ human-directed social skills. Dogs have a high social competence when it comes to humans. Two experiments commonly used to study these skills are the problem-solving test, where dogs’ human-directed behaviours when faced with a problem are measured, and the pointing test, where dogs are tested on how well they understand human gestures. We compared the social skills of German shepherds and Labrador retrievers, and of common- and field-type Labradors. Labradors were more successful in the pointing test and German shepherds stayed closer to their owners during the problem solving. Among Labrador types, the field type had more human eye contact than the common type. Importantly, when comparing the two experiments, we found no positive correlations between the problem-solving test and the pointing test, suggesting that the two tests measure different aspects of human-directed social behaviour in dogs.

A previous study has identified two suggestive genetic regions for human-directed social behaviours during the problem-solving test in beagles. In paper III, we show that these SNPs are also associated to social behaviours in Labrador and golden retrievers. Moreover, the Labrador breed types differed significantly in allele frequencies. This indicates that the two SNPs have been affected by recent selection and may have a part in the differences in sociability between common and field type.

The behaviour of dogs cannot simply be explained by genetics, there is also an environmental component. In paper IV, we study which factors that affect long-term stress in dogs. Long-term cortisol can be measured by hair samples. We found a clear synchronization in hair cortisol concentrations between dogs and their owners. Neither dogs’ activity levels nor their behavioural traits affected the cortisol, however, the personality of the owners did. Therefore, we suggest that dogs mirror the stress level of their owners.

The mediator between genes and the environment is epigenetics, and one epigenetic factor is DNA methylation. In paper V, we compared methylation patterns of wolves and dogs as well as dog breeds. Between both wolves and dogs and among dogs there were substantial differences in methylated DNA regions, suggesting that DNA methylation is likely to contribute to the vast variation among canines. We hypothesize that epigenetic factors have been important during domestication and in breed formation.

In this thesis, I cover several aspects on how dogs’ behaviours can be affected, and paint an intricate picture on how genetics, epigenetics, and human-dog relations forms dog behaviour.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. , p. 49
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1989
National Category
Evolutionary Biology Zoology Behavioral Sciences Biology Genetics
Identifiers
URN: urn:nbn:se:liu:diva-156353DOI: 10.3384/diss.diva-156353ISBN: 9789176850725 (print)OAI: oai:DiVA.org:liu-156353DiVA, id: diva2:1305504
Public defence
2019-05-09, Planck, Fysikhuset, Campus Valla, Linköping, 09:15 (English)
Opponent
Supervisors
Available from: 2019-04-17 Created: 2019-04-17 Last updated: 2019-04-17Bibliographically approved
List of papers
1. Similar recent selection criteria associated with different behavioural effects in two dog breeds
Open this publication in new window or tab >>Similar recent selection criteria associated with different behavioural effects in two dog breeds
2016 (English)In: Genes, Brain and Behavior, ISSN 1601-1848, E-ISSN 1601-183X, Vol. 15, no 8, p. 750-756Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Wiley-Blackwell Publishing Inc., 2016
Keywords
Behavioural genetics, behavioural test, dog behaviour, dogs, golden retriever, heritability, Labrador retriever, selection
National Category
Evolutionary Biology Zoology Behavioral Sciences Biology Genetics
Identifiers
urn:nbn:se:liu:diva-132746 (URN)10.1111/gbb.12317 (DOI)000393079000007 ()27520587 (PubMedID)
Note

Funding agencies: research council, Formas; Advanced Research Grant from the European Research Council (ERC) [322206]

Available from: 2016-11-22 Created: 2016-11-22 Last updated: 2019-04-17Bibliographically approved
2. Understanding of human referential gestures is not correlated to human-directed social behaviour in Labrador retrievers and German shepherd dogs
Open this publication in new window or tab >>Understanding of human referential gestures is not correlated to human-directed social behaviour in Labrador retrievers and German shepherd dogs
Show others...
2018 (English)In: Applied Animal Behaviour Science, ISSN 0168-1591, E-ISSN 1872-9045, Vol. 201, p. 46-53Article in journal (Refereed) Published
Abstract [en]

Dogs are known to excel in interspecific communication with humans and both communicate with humans and follow human communicative cues. Two tests commonly used to test these skills are, firstly, the problem-solving paradigm, and, secondly, following human referential signals, for example pointing. The aim of the present study was to investigate whether dogs that seek more human contact in an unsolvable problem-solving paradigm also better understand human communicative cues in a pointing test. We also assessed between- and within-breed variation in both tests. 167 dogs were tested and were of the breeds German shepherd dog and Labrador retriever. The Labradors were separated into the two selection lines: common type (bred for show and pet) and field type (bred for hunting). A principal component analysis of behaviours during the problem solving revealed four components: Passivity, Experimenter Contact, Owner Contact and Eye Contact. We analysed the effect of these components on success rate in the pointing test and we found no effect for three of them, while a negative correlation was found for Owner Contact (F(1,147) = 6.892; P = 0.010). This was only present in common-typed Labradors. We conclude that the ability to follow a pointing cue does not predict the propensity for human-directed social behaviour in a problem-solving situation and suggest that the two tests measure different aspects of human-directed social behaviour in dogs.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Human-dog communication, Human-directed social behaviour, Pointing test, Problem-solving test, German shepherd dogs. Labrador retrievers
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-145542 (URN)10.1016/j.applanim.2017.12.017 (DOI)000430774800007 ()2-s2.0-85039704233 (Scopus ID)
Note

Funding agencies: European Research Council (ERC) [322206]

Available from: 2018-03-05 Created: 2018-03-05 Last updated: 2019-04-17Bibliographically approved
3. Sociality genes are associated with human-directed social behaviour in golden and Labrador retriever dogs
Open this publication in new window or tab >>Sociality genes are associated with human-directed social behaviour in golden and Labrador retriever dogs
Show others...
2018 (English)In: PeerJ, ISSN 2167-8359, E-ISSN 2167-8359, Vol. 6, article id e5889Article in journal (Refereed) Published
Abstract [en]

Background: Dogs have human-directed social skills that allow them to communicate and cooperate with humans. We have previously identified two loci on chromosome 26 associated with human contact-seeking behaviors during an unsolvable problem task in laboratory beagles (Persson et A, 2016). The aim of the present study was to verify the single nucleotide polymorphisms (SNPs) in additional dog breeds. We also studied how the allele frequencies have changed during domestication and recent selection. Methods: Dogs of two breeds, 61 golden retrievers and 100 Labrador retrievers, were phenotyped and genotyped, and 19 wolves were genotyped. The Labrador retrievers were divided into common and field type by pedigree data to make it possible to study the effects of recent selection. All dogs were tested in an unsolvable problem task where human-directed social behaviors were scored. DNA from dogs (buccal swabs) and wolves (blood or brain tissue) was analyzed for genotype on two of the previously identified SNP markers, BICF2G630798942 (SNP1) and BICF2S23712114 (SNP2), by pyrosequencing. Results: There was genetic variation for SNP1 in both dog breeds whereas the wolves were fixed for this polymorphism, and for SNP2 there was variation in both dogs and wolves. For both SNPs, Labrador retriever types differed significantly in allele frequencies. We found associations between SNPs and human-directed social behavior in both dog breeds. In golden retrievers, SNP I was associated with physical contact variables, for example, with the duration of physical contact with the owner (F-2,F-56 = 4.389, p = 0.017). SNP2 was associated with several behavioral variables in both breeds, among others owner gazing frequency in both golden retrievers (F-2,F-55 = 6.330, p = 0.003) and Labradors (F-1,F-93 = 5.209, p = 0.025). Discussion: Our results verify the association between the previously identified SNPs and human-directed social behavior scored in an unsolvable problem task. Differences in allele frequencies suggest that these loci have been affected by selection. The results indicate that these genomic regions are involved in human-directed social behavior in not only beagles but in other dog breeds as well. We hypothesize that they may have been important during dog domestication.

Place, publisher, year, edition, pages
PEERJ INC, 2018
Keywords
Genetics; Dog genetics; Dog behavior; Human-dog communication; Human-directed social behavior; Golden retrievers; Labrador retrievers; Wolf; Domestication; Behavior genetics
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:liu:diva-153536 (URN)10.7717/peerj.5889 (DOI)000452327000008 ()30416887 (PubMedID)
Note

Funding Agencies|European Research Council (ERC) [322206]

Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2019-04-17

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Sundman, Ann-Sofie

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