Behavioural correlations of the domestication syndrome are decoupled in modern dog breeds

Selection for tameness alters play-like behaviour in red junglefowl in line with effects of domestication

The phenotypic alterations brought by domestication have been hypothesized to be driven by selection for tameness. To explore this, we selected red junglefowl (RJF) for high (HF) and low (LF) fear of humans for 14 generations. We previously found that domesticated chickens performed more play-like behaviours during early ontogeny, and therefore, in this study, we explored potential effects of tameness. Groups of three to four chicks were randomly created from each selection line, and each group was moved to an enriched play arena twice per week, from day 6 until day 53 post-hatch. The frequency of 14 different play-like behaviours, categorized as locomotor, social and object play-like behaviour were recorded for 30 min at every observation instance. Every group of three or four birds constituted the independent statistical replicates and measures were averaged within the groups. The frequency of total play-like behaviour as well as object, and locomotor play-like behaviour was significantly higher in LF, while social play-like behaviour was significantly more common in HF. This largely mirrors previous observations of differences between domesticated and ancestral chickens. Hence, our results support the important role of tameness for the evolution of domesticated behaviour.

Behavioural differences and similarities between dog breeds: proposing an ecologically valid approach for canine behavioural research

The behaviour of dogs holds great relevance for not only scientists from fundamental and applied research areas, but also due to the widespread roles of dogs in our societies as companions and working animals; their behaviour is also an important factor in animal and human welfare. A large proportion of dogs currently under human supervision belong to one of roughly 400 recognised breeds. Dog breeds can be characterised by distinctive, predictable and reproducible features, including some of their behavioural traits. To the scientist, the comparative analysis of the behaviour of dog breeds provides an opportunity for investigating an array of intriguing phenomena within an easily accessible model organism created from natural and human-driven evolutionary processes. There are many ways to design and conduct breed-related behavioural investigations, but such endeavours should always be based around biologically relevant research questions and lead to ecologically valid conclusions. In this review, we surveyed recent research efforts that included dog behaviour-related comparisons and applied a critical evaluation according to their methods of breed choice and the subsequent research design. Our aim was to assess whether these two fundamentally important components of experimental design provide a solid basis to reach valid conclusions. Based on 97 publications that fulfilled our selection criteria, we identified three primary methods used by researchers to select breeds for their investigations: (i) convenience sampling; (ii) hypothesis-driven, ancestry-based sampling; and (iii) hypothesis-driven, functional sampling. By using the SWOT (Strengths, Weaknesses, Opportunities, Threats) evaluation system, we highlight each of these techniques' merits and shortcomings. We identify when particular methods may be inherently unable to produce biologically meaningful results due to a mismatch between breed choice and the initial research goals. We hope that our evaluation will help researchers adopt best practices in experimental design regarding future dog breed comparisons.

Whole-genome resequencing to investigate the genetic diversity and mechanisms of plateau adaptation in Tibetan sheep

INTRODUCTION

Tibetan sheep, economically important animals on the Qinghai-Tibet Plateau, have diversified into numerous local breeds with unique characteristics through prolonged environmental adaptation and selective breeding. However, most current research focuses on one or two breeds, and lacks a comprehensive representation of the genetic diversity across multiple Tibetan sheep breeds. This study aims to fill this gap by investigating the genetic structure, diversity and high-altitude adaptation of 6 Tibetan sheep breeds using whole-genome resequencing data.

RESULTS

Six Tibetan sheep breeds were investigated in this study, and whole-genome resequencing data were used to investigate their genetic structure and population diversity. The results showed that the 6 Tibetan sheep breeds exhibited distinct separation in the phylogenetic tree; however, the levels of differentiation among the breeds were minimal, with extensive gene flow observed. Population structure analysis broadly categorized the 6 breeds into 3 distinct ecological types: plateau-type, valley-type and Euler-type. Analysis of unique single-nucleotide polymorphisms (SNPs) and selective sweeps between Argali and Tibetan sheep revealed that Tibetan sheep domestication was associated primarily with sensory and signal transduction, nutrient absorption and metabolism, and growth and reproductive characteristics. Finally, comprehensive analysis of selective sweep and transcriptome data suggested that Tibetan sheep breeds inhabiting different altitudes on the Qinghai-Tibet Plateau adapt by enhancing cardiopulmonary function, regulating body fluid balance through renal reabsorption, and modifying nutrient digestion and absorption pathways.

CONCLUSION

In this study, we investigated the genetic diversity and population structure of 6 Tibetan sheep breeds in Qinghai Province, China. Additionally, we analyzed the domestication traits and investigated the unique adaptation mechanisms residing varying altitudes in the plateau region of Tibetan sheep. This study provides valuable insights into the evolutionary processes of Tibetan sheep in extreme environments. These findings will also contribute to the preservation of genetic diversity and offer a foundation for Tibetan sheep diversity preservation and plateau animal environmental adaptation mechanisms.

Independent, but still observant-dog breeds selected for functional independence learn better from a conspecific demonstrator than cooperative breeds in a detour task

BACKGROUND

While complex dog-human coexistence has been deeply investigated, there is a relative scarcity of similar knowledge regarding dog-dog interactions. Social learning, a fundamental synchronizing mechanism between dogs and humans, was recently found to be influenced by the functional breed selection of dogs: with the cooperative breeds being more effective learners from a human demonstrator than the independent working breeds were. Here, we investigated whether these differences would also be present when dogs had to learn from another dog and how to effectively perform a detour around a transparent V-shaped obstacle. We tested dogs from 28 independent and 19 cooperative breeds in three consecutive trials. In the control groups, all dogs had to detour on their own the obstacle. In the dog demonstration groups, in trial 1, the subjects had to detour on their own, but before the next two trials, a trained dog showed them the solution.

RESULTS

We found that the performance of the two breed groups was the same in the without demonstration groups. However, after observing the dog demonstrator, the independent dogs learned the task more successfully than the cooperative breeds did. In the case of the independent working breeds, detour latencies significantly dropped along the consecutive trials, and these dogs also showed higher rate of successful detours after observing the demonstrator dog's action than in the control group.

CONCLUSIONS

This is the first study where the consequences of functional breed selection were confirmed in a scenario that involved conspecific social learning in dogs. The results fit well to the ecologically valid framework of the evolutionary past of dog breed formation, in which cooperative breeds were selected for their interactivity with humans, whereas independent breeds often had to work together with their conspecifics.

Identification of novel genetic loci related to dromedary camel (Camelus dromedarius) morphometrics, biomechanics, and behavior by genome-wide association studies

In the realm of animal breeding for sustainability, domestic camels have traditionally been valued for their milk and meat production. However, key aspects such as zoometrics, biomechanics, and behavior have often been overlooked in terms of their genetic foundations. Recognizing this gap, the present study perfomed genome-wide association analyses to identify genetic markers associated with zoometrics-, biomechanics-, and behavior-related traits in dromedary camels (Camelus dromedarius). 16 and 108 genetic markers were significantly associated (q < 0.05) at genome and chromosome-wide levels of significance, respectively, with zoometrics- (width, length, and perimeter/girth), biomechanics- (acceleration, displacement, spatial position, and velocity), and behavior-related traits (general cognition, intelligence, and Intelligence Quotient (IQ)) in dromedaries. In most association loci, the nearest protein-coding genes are linkedto neurodevelopmental and sensory disorders. This suggests that genetic variations related to neural development and sensory perception play crucial roles in shaping a dromedary camel's physical characteristics and behavior. In summary, this research advances our understanding of the genomic basis of essential traits in dromedary camels. Identifying specific genetic markers associated with zoometrics, biomechanics, and behavior provides valuable insights into camel domestication. Moreover, the links between these traits and genes related to neurodevelopmental and sensory disorders highlight the broader implications of domestication and modern selection on the health and welfare of dromedary camels. This knowledge could guide future breeding strategies, fostering a more holistic approach to camel husbandry and ensuring the sustainability of these animals in diverse agricultural contexts.

Making fetch happen: Prevalence and characteristics of fetching behavior in owned domestic cats (Felis catus) and dogs (Canis familiaris)

Both cats and dogs fetch, but the likely function(s) of this behavior for each species have not been compared. In this study, we assessed data from online surveys of cat and dog behavior (Fe-BARQ; C-BARQ) completed by cat (N = 8224) and dog owners (N = 73724). We assessed responses to the items "Plays 'fetch'; likes to retrieve thrown objects or toys" (Fe-BARQ) and "Will 'fetch' or attempt to fetch sticks, balls, or objects" (C-BARQ). Cats and dogs described as "sometimes," "usually" or "always" fetching were categorized as fetchers. Regression models were used to examine which animal-related (e.g., sex, age) and environmental factors best predicted fetching, and chi-square tests were used to explore the effect of breed on fetching behavior. Fetching was reported in 40.9% of cats and 77.8% of dogs. In cats, fetching was correlated with play and activity. In dogs, fetching was correlated with overall trainability. In both cats and dogs, being female, older, living with (other) dogs, and having health problems decreased the likelihood of fetching. Breed effects were observed in both species, with fetching more prominent in cat breeds originating in the Far East (e.g., Burmese, Siamese, and Tonkinese) and in dog breeds from the Retriever, UK Rural, Poodle, Pointer and Spaniel clades. We discuss the results in the context of domestication history of both cats and dogs and posit several hypotheses about why fetching behavior is observed in both.

You talkin' to me? Functional breed selection may have fundamentally influenced dogs' sensitivity to human verbal communicative cues

BACKGROUND

The ability to learn from humans via observation was considered to be equally present across properly socialized dogs. We showed recently that cooperative working breeds learned from a human demonstrator more effectively. We hypothesized that functional breed selection could affect sensitivity to human attention-eliciting behavior. Accordingly, we ran the first ever study on dogs that compared the effect of ostensive and neutral verbal communication in a social learning scenario. We used the detour paradigm around a transparent V-shaped fence with either ostensive (addressing the receiver both with words and specific, attention-eliciting prosody) or neutral speech (monotonous reciting of a short poem) demonstration. The other features (gestures, movement) of the demonstration sequence were kept identical between the two conditions. We tested (N = 70) companion dogs from 17 cooperative and 16 independent breeds in three 1-min trials. Subjects had to obtain the reward by detouring around the fence.

RESULTS

Detour latencies of the cooperative dogs improved after both ostensive and neutral speech demonstrations. The independent dogs did not improve their detour latency in either of the conditions. Remarkably, ostensive verbal utterances elicited longer relative looking time towards the demonstrator, cooperative dogs looked longer at the demonstrator, and longer looking time resulted in more successful detours.

CONCLUSIONS

Our study provides the first indication that functional breed selection had a significant impact on dogs' sensitivity to ostensive human communication, which, apart from being crucially important for social learning from humans, until now was considered as a uniformly present heritage of domestication in dogs.

Cooperative but Dependent-Functional Breed Selection in Dogs Influences Human-Directed Gazing in a Difficult Object-Manipulation Task

It is still largely unknown to what extent domestication, ancestry, or recent functional selection are responsible for the behavioral differences in whether dogs look back to a human when presented with a difficult task. Here, we tested whether this ubiquitous human-related response of companion dogs would appear differently in subjects that were selected for either cooperative or independent work tasks. We tested N = 71 dogs from 18 cooperative and 18 independent breeds. Subjects learned in a five-trial warming-up phase that they could easily obtain the reward from a container. In trial six, the reward became impossible to take out from the locked container. When the task was easy, both breed groups behaved similarly, and their readiness to approach the container did not differ between the last 'solvable' and the subsequent 'unsolvable' trial. Task focus, looking at the container, touching the container for the first time, or interacting with the container with a paw or nose did not differ between the breed groups, indicating that their persistence in problem solving was similar. However, in the 'unsolvable' trial, cooperative dogs alternated their gaze more often between the container and the humans than the independent dogs did. The frequency of looking back was also higher in cooperative dogs than in the independent breeds. These are the first empirical results that suggest, in a balanced, representative sample of breeds, that the selection for different levels of cooperativity in working dogs could also affect their human-dependent behavior in a generic problem-solving situation.

The reduction in relative brain size in the domesticated dog is not an evolutionary singularity among the canids

Domestication has long been considered the most powerful evolutionary engine behind dramatic reductions in brain size in several taxa, and the dog (Canis familiaris) is considered as a typical example that shows a substantial decrease in brain size relative to its ancestor, the grey wolf (Canis lupus). However, to make the case for exceptional evolution of reduced brain size under domestication requires an interspecific approach in a phylogenetic context that can quantify the extent by which domestication reduces brain size in comparison to closely related non-domesticated species responding to different selection factors in the wild. Here, we used a phylogenetic method to identify evolutionary singularities to test if the domesticated dog stands out in terms of relative brain size from other species of canids. We found that the dog does not present unambiguous signature of evolutionary singularity with regard to its small brain size, as the results were sensitive to the considerations about the ancestral trait values upon domestication. However, we obtained strong evidence for the hibernating common raccoon dog (Nyctereutes procyonoides) being an evolutionary outlier for its brain size. Therefore, domestication is not necessarily an exceptional case concerning evolutionary reductions in brain size in an interspecific perspective.

Street-wise dog testing: Feasibility and reliability of a behavioural test battery for free-ranging dogs in their natural habitat

Behavioural scientists are increasingly recognizing the need to conduct experiments in the wild to achieve a comprehensive understanding of their species' behaviour. For domestic dogs (Canis familiaris), such progress has been slow. While the life in human households is often regarded as dogs' natural habitat, this classification disregards most of the global dog population. The value of experimentally testing free-ranging dogs' cognition and behaviour is increasingly being recognized, but no comprehensive test batteries have been conducted on those populations so far, leaving the feasibility and reliability of such endeavours unknown. This study is the starting point to fill this gap by pioneering and validating an elaborate behavioural test battery on street-living dogs. Therein, six common temperament tests (human-/conspecific-directed sociability, neophobia, tractability) and dog-human communication paradigms (pointing, inaccessible object) were adapted to the street conditions. We evaluated the feasibility of the test battery, the coding reliability of the measures, and investigated their temporal consistency in a retest of the same individuals six weeks later (test-retest reliability). The test battery proved feasible with most dogs participating in all subtests, and it showed satisfactory inter- and intra-rater reliability (0.84 and 0.93 respectively), providing evidence that complex behavioural tests can be conducted even in highly variable street conditions. Retesting revealed that some behaviours could be captured reliably across time, especially when the subtest was particularly engaging (e.g., human approach, point following). In contrast, the low retest reliability for subtests relying on sustained novelty and behaviours that were highly susceptible to disturbances (e.g., gazing) reflects the difficulties of street dog testing, including standardisation in disturbance-prone environments, ecology-dependent adaptation of methods, and intrinsic differences between pet and free-ranging dogs. With some adaptations, this test battery can be valuable in investigating cognition and behavioural profiles in such an understudied population as free-ranging dogs.

Association of tameness and sociability but no sign of domestication syndrome in mice selectively bred for active tameness

Domesticated animals have been developed by selecting desirable traits following the initial unconscious selection stage, and now exhibit phenotypes desired by humans. Tameness is a common behavioural trait found in all domesticated animals. At the same time, these domesticated animals exhibit a variety of morphological, behavioural, and physiological traits that differ from their wild counterparts of their ancestral species. These traits are collectively referred to as domestication syndrome. However, whether this phenomenon exists is debatable. Previously, selective breeding has been used to enhance active tameness, a motivation to interact with humans, in wild heterogeneous stock mice derived from eight wild inbred strains. In the current study, we used tame mice to study how selective breeding for active tameness affects behavioural and morphological traits. A series of behavioural and morphological analyses on mice showed an increased preference for social stimuli and a longer duration of engagement in non-aggressive behaviour. However, no differences were observed in exploratory or anxiety-related behaviours. Similarly, selection for tameness did not affect ultrasonic vocalisations in mice, and no changes were observed in known morphological traits associated with domestication syndrome. These results suggest that there may be a link between active tameness and sociability and provide insights into the relationship between tameness and other behaviours in the context of domestication.

Domestication and breeding objective did not shape the interpretation of physical and social cues in goats (Capra hircus)

Artificial selection by humans, either through domestication or subsequent selection for specific breeding objectives, drives changes in animal cognition and behaviour. However, most previous cognitive research comparing domestic and wild animals has focused on companion animals such as canids, limiting any general claims about the effects of artificial selection by humans. Using a cognitive test battery, we investigated the ability of wild goats (non-domestic, seven subjects), dwarf goats (domestic, not selected for milk production, 15 subjects) and dairy goats (domestic, selected for high milk yield, 18 subjects) to utilise physical and social cues in an object choice task. To increase the heterogeneity of our test samples, data for domestic goats were collected by two experimenters at two research stations (Agroscope; Research Institute for Farm Animal Biology). We did not find performance differences between the three groups in the cognitive test battery for either physical or social cues. This indicates that for a domestic non-companion animal species, domestication and selection for certain breeding objectives did not measurably shape the physical and cognitive skills of goats.

Children's interaction with a dog when having Animal Assisted Activity in paediatric hospital care

The aim of the study was to investigate the interaction process between child and dog and how it possibly affects children's wellbeing during Animal Assisted Activity. Children have reported negative feelings such as fear and anxiety when being cared for in hospital and various kinds of complementary treatment can alleviate this. Different complementary treatments, including interaction with a dog, can create positive emotions and the treatment has been reported to have both physiological and psychological beneficial effects. However, there is a lack of studies describing children's interaction with a dog. This is an observational study, analysed from field notes with qualitative content analysis using a deductive approach. Children (n = 49) aged 3-18 years of age at a paediatric hospital voluntarily participated in the study. The results are reported on a six-level scale that describes the child-dog interaction: 1. Passive interaction, 2. One-way non-spoken communication, 3. Facilitating the interaction, 4. Interaction by activity encouragement, 5. Interaction initiated by the child, and 6. Interaction through deepened interplay. All children attained level five. Eighty-nine per cent attained level six and these children interacted fully, having a two-way deepened interplay with the dog. Further, when the interaction proceeded to a deepened interplay this affected the children positively both physically and emotionally. Structured Animal Assisted Activity with a dog that includes an introduction, an active part and a relaxing part is a suitable model to offer children in paediatric hospital care since the children attained a child-initiated interaction or interaction through deepened interplay.

Exploring the Domestication Syndrome Hypothesis in Dogs: Pigmentation Does Not Predict Cortisol Levels

Previous research has found connections between pigmentation, behavior, and the physiological stress response in both wild and domestic animals; however, to date, no extensive research has been devoted to answering these questions in domestic dogs. Modern dogs are exposed to a variety of stressors; one well-studied stressor is residing in an animal shelter. To explore the possible relationships between dogs' responses to stress and their pigmentation, we conducted statistical analyses of the cortisol:creatinine ratios of 208 American shelter dogs as a function of their coat color/pattern, eumelanin pigmentation, or white spotting. These dogs had been enrolled in previous welfare studies investigating the effect of interventions during which they left the animal shelter and spent time with humans. In the current investigation, we visually phenotype dogs based on photographs in order to classify their pigmentation and then conduct post hoc analyses to examine whether they differentially experience stress as a function of pigmentation. We found that the dogs did not differ significantly in their urinary cortisol:creatinine ratios based on coat color/pattern, eumelanin pigmentation, or white spotting, either while they were residing in the animal shelter or during the human interaction intervention. These preliminary data suggest that pigmentation alone does not predict the stress responses of shelter dogs; however, due to the small sample size and retrospective nature of the study, more research is needed.

Potential domestication and tameness effects on prosocial behaviour in chickens

Prosocial behaviour is pronounced in humans and prevalent in some non-human animals, however, the occurrence of the trait in chickens has not yet been investigated. Here, we studied the occurrence of prosociality in four different lines of adult female chickens. To explore the effects of domestication, chickens of the domesticated layer White Leghorn (WL) and the ancestral Red Junglefowl (RJF) were compared. Additionally, to explore the role of tameness, Red Junglefowl selected for high (RJF HF), or low (RJF LF) fear of humans were also studied. The hens were all tested in a prosocial choice task adapted from a previous study conducted on rats. Each individual was first trained to differentiate between a compartment where itself and a companion received food treats simultaneously (representing a prosocial choice), and one where only itself received the treat. Following training, each bird was tested in a free-choice set-up. No occurrence of prosociality was found at group level in any of the lines, however, our results suggest that the trait may occur in some individuals, and that domestication and increased tameness may have increased its prevalence, although alternative explanations such as side bias and social competition cannot be ruled out. Since this study is the first of its kind, further research is required to make any definite conclusions.

Would You Detour with Me? Association between Functional Breed Selection and Social Learning in Dogs Sheds Light on Elements of Dog-Human Cooperation

Interspecific social learning is a main synchronizing mechanism that enables dogs to adapt to the anthropogenic niche. It is not known whether dogs in general possess the capacity of learning from humans or whether more recent selective events have affected their ability to learn from humans. We hypothesized that cooperative and independent working dog breeds may behave differently in a social learning task. Dogs (N = 78 from 16 cooperative and 18 independent breeds) had to detour a transparent, V-shaped wire mesh fence. The experiment consisted of three one-minute-long trials. The control condition did not include a demonstration. In the demonstration condition, the experimenter placed a reward in the inside corner by walking around the fence. Cooperative dogs reached the target significantly faster, while independent dogs did not detour faster in trials 2 and 3 after the human demonstration. Detour latencies were not associated with the keeping conditions and training level of the subjects. As we assembled both test groups from several genetically distantly related breeds, we can exclude the explanation that higher cooperativity emerged only in particular clades of dogs; instead, functional selection for particular working tasks could enhance capacities that affect a wide range of socio-cognitive traits in dogs.

Shared reproductive disruption, not neural crest or tameness, explains the domestication syndrome

Altered neural crest cell (NCC) behaviour is an increasingly cited explanation for the domestication syndrome in animals. However, recent authors have questioned this explanation, while others cast doubt on whether domestication syndrome even exists. Here, we review published literature concerning this syndrome and the NCC hypothesis, together with recent critiques of both. We synthesize these contributions and propose a novel interpretation, arguing shared trait changes under ancient domestication resulted primarily from shared disruption of wild reproductive regimes. We detail four primary selective pathways for 'reproductive disruption' under domestication and contrast these succinct and demonstrable mechanisms with cryptic genetic associations posited by the NCC hypothesis. In support of our perspective, we illustrate numerous important ways in which NCCs contribute to vertebrate reproductive phenotypes, and argue it is not surprising that features derived from these cells would be coincidentally altered under major selective regime changes, as occur in domestication. We then illustrate several pertinent examples of Darwin's 'unconscious selection' in action, and compare applied selection and phenotypic responses in each case. Lastly, we explore the ramifications of reproductive disruption for wider evolutionary discourse, including links to wild 'self-domestication' and 'island effect', and discuss outstanding questions.

Following the human point: Research with nonhuman animals since Povinelli, Nelson, and Boysen (1990)

For this special issue in honor of Dr. Sarah (Sally) Boysen's career, we review studies on point following in nonhuman animals. Of the 126 papers that we documented on this topic published since the publication of Povinelli, Nelson, and Boysen (1990, Journal of Comparative Psychology, 104, 203-210), 94 (75%) were published in the past 15 years, including 22 in the past 5 years, indicating that this topic is still an active area of interest in the field of animal behavior and cognition. We present results of a survey of publication trends, discussing the species tested and the sample sizes, and we note methodological considerations and current multilaboratory approaches. We then categorize and synthesize the research questions addressed in these studies, which have been at both the ultimate level (e.g., questions related to evolutionary adaptiveness and phylogenetic differences) and proximate level (e.g., questions related to experiential and temperamental processes). Throughout, we consider future directions for this area of research.

Genetic distance from wolves affects family dogs' reactions towards howls

Domestication dramatically changes behaviour, including communication, as seen in the case of dogs (Canis familiaris) and wolves (Canis lupus). We tested the hypothesis that domestication may affect an ancient, shared communication form of canids, the howling which seems to have higher individual variation in dogs: the perception and usage of howls may be affected by the genetic relatedness of the breeds to their last common ancestor with wolves ('root distance') and by other individual features like age, sex, and reproductive status. We exposed 68 purebred dogs to wolf howl playbacks and recorded their responses. We identified an interaction between root distance and age on the dogs' vocal and behavioural responses: older dogs from more ancient breeds responded longer with howls and showed more stress behaviours. Our results suggest that domestication impacts vocal behaviour significantly: disintegrating howling, a central, species-specific communication form of canids and gradually eradicating it from dogs' repertoire.

Zoonotic parasites associated with predation by dogs and cats

One of the most common behaviors of cats that have an indoor/outdoor lifestyle is to bring hunted "gifts" to their owners, represented by small mammals, reptiles and birds. Access to the outdoors by dogs and cats may represent a problematic issue, since they may be at risk of diseases, traffic accidents and ingestion of toxins. Yet, the impact of this population of roaming dogs and cats predating wildlife is another concerning issue that receives less attention. Despite these risks, most owners still prefer to give outdoor access to their pets to allow them to express their "natural instincts," such as hunting. Therefore, with a growing population of > 470 million dogs and 373 million cats worldwide, predation not only represents a threat to wildlife, but also a door of transmission for parasitic diseases, some of them of zoonotic concern. In this review, the role played by dogs, and especially cats, in the perpetuation of the biological life cycle of zoonotic parasites through the predation of rodents, reptiles and birds is discussed. Feral and domestics dogs and cats have contributed to the population collapse or extinction of > 63 species of reptiles, mammals and birds. Although the ecological impact of predation on wild populations is well documented, the zoonotic risk of transmission of parasitic diseases has not received significant attention. The parasitic diseases associated to predation vary from protozoan agents, such as toxoplasmosis, to cestodes like sparganosis and even nematodes such as toxocariasis. Raising awareness about predation as a risk of zoonotic parasitic infections in dogs and cats will aid to create responsible ownership and proper actions for controlling feral and free-roaming cat and dog populations worldwide.

baz1b loss-of-function in zebrafish produces phenotypic alterations consistent with the domestication syndrome

BAZ1B is a ubiquitously expressed nuclear protein with roles in chromatin remodeling, DNA replication and repair, and transcription. Reduced BAZ1B expression disrupts neuronal and neural crest development. Variation in the activity of BAZ1B has been proposed to underly morphological and behavioral aspects of domestication through disruption of neural crest development. Knockdown of baz1b in Xenopus embryos and Baz1b loss-of-function (LoF) in mice leads to craniofacial defects consistent with this hypothesis. We generated baz1b LoF zebrafish using CRISPR/Cas9 gene editing to test the hypothesis that baz1b regulates behavioral phenotypes associated with domestication in addition to craniofacial features. Zebrafish with baz1b LoF show mild underdevelopment at larval stages and distinctive craniofacial features later in life. Mutant zebrafish show reduced anxiety-associated phenotypes and an altered ontogeny of social behaviors. Thus, in zebrafish, developmental deficits in baz1b recapitulate both morphological and behavioral phenotypes associated with the domestication syndrome in other species.

Does the Domestication Syndrome Apply to the Domestic Pig? Not Completely

The ‘domestication syndrome’ defines a suite of features that domesticated animals possess as the result of the artificial selection operated by Homo sapiens since the Neolithic. An interesting anthropological question is whether such features, including increased tameness and reduced aggression, apply to all domesticated forms. We investigated this issue in the domestic pig (Sus scrofa). We video-recorded and analysed aggression and social play (mostly play-fighting) sessions from piglets (three litters; n = 24) and wild boar hybrids (domestic pig mother x wild boar father; three litters; n = 27) from 6–50 days of age, raised in the same woodland/grassland habitat and extensive farming management (ethical farm ‘Parva Domus’, Cavagnolo, Torino). Play and aggression session structure was assessed via Asymmetry (AI; offensive/defensive pattern balance), Shannon (H′; pattern variability), and Pielou (J; pattern evenness) indices. We found that piglets played more (especially after the 20th day of life) and engaged in less variable and uniform sessions than wild boar hybrids. Compared to hybrids, piglets showed less variable but more frequent (especially when approaching weaning) and asymmetrical aggressive events. Thus, the domestication syndrome does not seem to fully apply to either social play or aggression, possibly because artificial selection has produced greater tameness of pigs towards humans than towards conspecifics.

Eye contact and sociability data suggests that Australian dingoes were never domesticated

Dogs were the first animal to become domesticated by humans, and they represent a classic model system for unraveling the processes of domestication. We compare Australian dingo eye contact and socialization with Basenji and German Shepherd dog (GSD) breeds. Australian dingoes arrived in Australia 5,000-8,000 BP, and there is debate whether they were domesticated before their arrival. The Basenji represents a primitive breed that diverged from the remaining breeds early in the domestication process, while GSDs are a breed dog selected from existing domestic dogs in the late 1800s. We conducted a 4-phase study with unfamiliar and familiar investigators either sitting passively or actively calling each canid. We found 75% of dingoes made eye contact in each phase. In contrast, 86% of Basenjis and 96% of GSDs made eye contact. Dingoes also exhibited shorter eye-gaze duration than breed dogs and did not respond to their name being called actively. Sociability, quantified as a canid coming within 1 m of the experimenter, was lowest for dingoes and highest for GSDs. For sociability duration, dingoes spent less time within 1 m of the experimenter than either breed dog. When compared with previous studies, these data show that the dingo is behaviorally intermediate between wild wolves and Basenji dogs and suggest that it was not domesticated before it arrived in Australia. However, it remains possible that the accumulation of mutations since colonization has obscured historical behaviors, and dingoes now exist in a feralized retamed cycle. Additional morphological and genetic data are required to resolve this conundrum.

Modularity patterns in mammalian domestication: Assessing developmental hypotheses for diversification

The neural crest hypothesis posits that selection for tameness resulted in mild alterations to neural crest cells during embryonic development, which directly or indirectly caused the appearance of traits associated with the "domestication syndrome" (DS). Although representing an appealing unitary explanation for the generation of domestic phenotypes, support for this hypothesis from morphological data and for the validity of the DS remains a topic of debate. This study used the frameworks of morphological integration and modularity to assess patterns that concern the embryonic origin of the skull and issues around the neural crest hypothesis. Geometric morphometric landmarks were used to quantify cranial trait interactions between six pairs of wild and domestic mammals, comprising representatives that express between five and 17 of the traits included in the DS, and examples from each of the pathways by which animals entered into relationships with humans. We predicted the presence of neural crest vs mesoderm modular structure to the cranium, and that elements in the neural crest module would show lower magnitudes of integration and higher disparity in domestic forms compared to wild forms. Our findings support modular structuring based on tissue origin (neural crest, mesoderm) modules, along with low module integration magnitudes for neural crest cell derived cranial elements, suggesting differential capacity for evolutionary response among those elements. Covariation between the neural crest and mesoderm modules accounted for major components of shape variation for most domestic/wild pairs. Contra to our predictions, however, we find domesticates share similar integration magnitudes to their wild progenitors, indicating that higher disparity in domesticates is not associated with magnitude changes to integration among either neural crest or mesoderm derived elements. Differences in integration magnitude among neural crest and mesoderm elements across species suggest that developmental evolution preserves a framework that promotes flexibility under the selection regimes of domestication.

Correlational selection in the age of genomics

Ecologists and evolutionary biologists are well aware that natural and sexual selection do not operate on traits in isolation, but instead act on combinations of traits. This long-recognized and pervasive phenomenon is known as multivariate selection, or-in the particular case where it favours correlations between interacting traits-correlational selection. Despite broad acknowledgement of correlational selection, the relevant theory has often been overlooked in genomic research. Here, we discuss theory and empirical findings from ecological, quantitative genetic and genomic research, linking key insights from different fields. Correlational selection can operate on both discrete trait combinations and quantitative characters, with profound implications for genomic architecture, linkage, pleiotropy, evolvability, modularity, phenotypic integration and phenotypic plasticity. We synthesize current knowledge and discuss promising research approaches that will enable us to understand how correlational selection shapes genomic architecture, thereby linking quantitative genetic approaches with emerging genomic methods. We suggest that research on correlational selection has great potential to integrate multiple fields in evolutionary biology, including developmental and functional biology, ecology, quantitative genetics, phenotypic polymorphisms, hybrid zones and speciation processes.

Two Ends of the Leash: Relations Between Personality of Shelter Volunteers and On-leash Walking Behavior With Shelter Dogs

Human personality influences the way people interact with dogs. This study investigated the associations between the personality of animal shelter volunteers and behavior during on-leash walks with shelter dogs. Video recording and a canine leash tension meter were used to monitor the on-leash walking. Personality was measured in five dimensions (neurotic, extroverted, open, agreeable and conscientious) with the NEO Five-Factor Inventory (NEO-FFI). Neurotic volunteers pulled the leash harder and tended to interact with dogs using more body language; dogs being walked by neurotic volunteers in turn displayed more lip-licking and body shaking and were more likely to be rated as well-behaved. Extroverted volunteers were associated with stronger maximal leash tension at both the human and dog ends of the leash, and they praised the dog more, often in a high pitched voice. These volunteers eliciting more tail-wagging and body shaking by the dog. Extroverted volunteers were also more tolerant of different dog behaviors. Volunteers with personalities characterized by "openness to experiences" were less likely to verbally attract the attention of dogs, praise dogs and talk to them in a high-pitched voice; however, dogs walked by these volunteers were more likely to pull on the leash, and engaged in more lip-licking but less sniffing. "Agreeable" volunteers liked to verbally attract the attention of the dogs and more commonly initiated hand gestures and physical contact, causing the dogs to pull less frequently; dogs in these dyads displayed more gazing and lip-licking behaviors. Conscientious volunteers were less likely to pull the leash and tended to have more physical contact with the dogs but did not favor verbal communication and did not use a high pitched voice.

Intraspecific variation in inhibitory motor control in guppies, Poecilia reticulata

Inhibitory control (IC) is the ability to overcome impulsive or prepotent but ineffective responses in favour of more appropriate behaviours. The ability to inhibit internal predispositions or external temptations is vital in coping with a complex and variable world. Traditionally viewed as cognitively demanding and a main component of executive functioning and self-control, IC was historically examined in only a few species of birds and mammals but recently a number of studies has shown that a much wider range of taxa rely on IC. Furthermore, there is growing evidence that inhibitory abilities may vary within species at the population and individual levels owing to genetic and environmental factors. Here we use a detour-reaching task, a standard paradigm to measure motor inhibition in nonhuman animals, to quantify patterns of interindividual variation in IC in wild-descendant female guppies, Poecilia reticulata. We found that female guppies displayed inhibitory performances that were, on average, half as successful as the performances reported previously for other strains of guppies tested in similar experimental conditions. Moreover, we showed consistent individual variation in the ability to inhibit inappropriate behaviours. Our results contribute to the understanding of the evolution of fish cognition and suggest that IC may show considerable variation among populations within a species. Such variation in IC abilities might contribute to individual differences in other cognitive functions such as spatial learning, quantity discrimination or reversal learning.

The link between selection for function and human-directed play behaviour in dogs

Human-directed play behaviour is a distinct behavioural feature of domestic dogs. But the role that artificial selection for contemporary dog breeds has played for human-directed play behaviour remains elusive. Here, we investigate how human-directed play behaviour has evolved in relation to the selection for different functions, considering processes of shared ancestry and gene flow among the different breeds. We use the American Kennel Club (AKC) breed group categorization to reflect the major functional differences and combine this with observational data on human-directed play behaviour for over 132 breeds across 89 352 individuals from the Swedish Dog Mentality Assessment project. Our analyses demonstrate that ancestor dogs already showed intermediate levels of human-directed play behaviour, levels that are shared with several modern breed types. Herding and Sporting breeds display higher levels of human-directed play behaviour, statistically distinguishable from Non-sporting and Toy breeds. Our results suggest that human-directed play behaviour played a role in the early domestication of dogs and that subsequent artificial selection for function has been important for contemporary variation in a behavioural phenotype mediating the social bond with humans.

Multivariate Analysis of Open Field Exploration Identifies Latent Spatial and Social Behavioral Axes in Domestic Dogs

Recent methodological advances in studying large scale animal movements have let researchers gather rich datasets from behaving animals. Often collected in small sample sizes due to logistical constraints, these datasets are however, ideal for multivariate explorations into behavioral complexity. In behavioral studies of domestic dogs, although automated data loggers have recently seen increasing use, a comprehensive framework to identify complex behavioral axes is lacking. Dog behavioral studies frequently rely on subjective ratings, despite demonstrable evidence that these are insufficient for identifying behavioral variables. Taking advantage of dogs’ innate running abilities and readily available GPS data loggers, we extracted latitude-longitude coordinates from running dogs in a large field setup. By extracting multiple variables from each logged coordinate, we generated a complex dataset from limited numbers of dog runs. Individual variables were successful in classifying aerobic competence, social awareness, and different exploratory patterns of dogs. Multivariate analyses identified latent features in movement patterns of dogs which were primarily comprised of two behavioral axes: spatial acuity and social awareness. Individual dogs were then behaviorally classified into independent clusters through unsupervised learning. Interestingly, even though field dogs clustered primarily with each other in varying degrees of energetic exploration and handler focus, some house pets displayed moderately high exploration abilities as well. We expect our proof of principle quantitative pipeline to provide a robust framework for behavioral classification, generating case-control clusters based solely on complex behavioral axes, and greatly benefiting genetic association studies of dog behavior.

Morphology does not covary with predicted behavioral correlations of the domestication syndrome in dogs

Domesticated animals display suites of altered morphological, behavioral, and physiological traits compared to their wild ancestors, a phenomenon known as the domestication syndrome (DS). Because these alterations are observed to co-occur across a wide range of present day domesticates, the traits within the DS are assumed to covary within species and a single developmental mechanism has been hypothesized to cause the observed co-occurrence. However, due to the lack of formal testing it is currently not well-resolved if the traits within DS actually covary. Here, we test the hypothesis that the presence of the classic morphological domestication traits white pigmentation, floppy ears, and curly tails predict the strength of behavioral correlations in support of the DS in 78 dog breeds. Contrary to the expectations of covariation among DS traits, we found that morphological traits did not covary among themselves, nor did they predict the strength of behavioral correlations among dog breeds. Further, the number of morphological traits in a breed did not predict the strength of behavioral correlations. Our results thus contrast with the hypothesis that the DS arises due to a shared underlying mechanism, but more importantly, questions if the morphological traits embedded in the DS are actual domestication traits or postdomestication improvement traits. For dogs, it seems highly likely that strong selection for breed specific morphological traits only happened recently and in relation to breed formation. Present day dogs therefore have limited bearing of the initial selection pressures applied during domestication and we should reevaluate our expectations of the DS accordingly.

The role of common ancestry and gene flow in the evolution of human-directed play behaviour in dogs

Among-population variance of phenotypic traits is of high relevance for understanding evolutionary mechanisms that operate in relatively short timescales, but various sources of nonindependence, such as common ancestry and gene flow, can hamper the interpretations. In this comparative analysis of 138 dog breeds, we demonstrate how such confounders can independently shape the evolution of a behavioural trait (human-directed play behaviour from the Dog Mentality Assessment project). We combined information on genetic relatedness and haplotype sharing to reflect common ancestry and gene flow, respectively, and entered these into a phylogenetic mixed model to partition the among-breed variance of human-directed play behaviour while also accounting for within-breed variance. We found that 75% of the among-breed variance was explained by overall genetic relatedness among breeds, whereas 15% could be attributed to haplotype sharing that arises from gene flow. Therefore, most of the differences in human-directed play behaviour among breeds have likely been caused by constraints of common ancestry as a likely consequence of past selection regimes. On the other hand, gene flow caused by crosses among breeds has played a minor, but not negligible role. Our study serves as an example of an analytical approach that can be applied to comparative situations where the effects of shared origin and gene flow require quantification and appropriate statistical control in a within-species/among-population framework. Altogether, our results suggest that the evolutionary history of dog breeds has left remarkable signatures on the among-breed variation of a behavioural phenotype.

Endocrine Regulations in Human-Dog Coexistence through Domestication

Endocrine system regulation is important for the maintenance of homeostasis; it controls hormonal functions in complex physiology and behavior and adaptations to social environments. Evidence indicates that for more than 35 000 years, dogs (Canis familiaris) have been domesticated through living with humans. For example, they have acquired human-like social skills, such as eye gazing and pointing gestures. These unique behaviors are, at least partially, regulated by hormones and are thought to have been genetically altered throughout domestication. Glucocorticoids affect social tolerance, while oxytocin facilitates social coordination and familiarity between individuals. We review historical and recent literature to facilitate an understanding of the roles of glucocorticoid and oxytocin functions in the human-canine coexistence dynamic established during domestication.