Appeasement function of displacement behaviours? Dogs' behavioural displays exhibited towards threatening and neutral humans.

Appeasement signals are behavioural patterns displaying an animal's non-aggressive attitude and are hypothesized to reduce the aggressive behaviours in the receiver. In domestic dogs, specific displacement behaviours (i.e., behavioural patterns exhibited without an apparent function related to the ongoing situation), have been suggested to function as appeasement signals. To test this possibility, we assessed whether the occurrence of these behaviours was dependent on a social conflict context, predicting that, if displacement behaviours also function as appeasement signals, they should be more prevalent in a conflict vs. non-conflict context. Fifty-three dogs were exposed to two unfamiliar humans approaching them in either a mildly threatening or neutral way. We categorized the attitude of the dogs towards the strangers as "reactive", i.e., barking and lunging towards the stimulus, and "non-reactive", i.e., remaining passive in front of the stimuli. We coded dogs' displacement activities and modelled their duration or frequency as a function of the interaction between the test condition and the attitude of the dog. Displacement behaviours of "blinking", "nose licking" and "lip wiping" were associated with a "non-reactive" attitude, independently from the test condition, confirming an association with a non-aggressive intention. "Head turning" was associated with a "non-reactive" attitude in the threatening condition. In conclusion, dogs with a non-aggressive attitude exhibited more putative appeasement signals; however, these were not strictly associated with a conflict-ridden situation, calling for further investigation of their function.

Why do dogs look back at the human in an impossible task? Looking back behaviour may be over-interpreted.

The impossible task paradigm has been extensively used to study the looking back behaviour in dogs. This behaviour is commonly considered a social problem-solving strategy: dogs facing an unsolvable task, soon give up and look back at the experimenter to ask for help. We aimed to test if the looking back in an impossible task does indeed represent a social problem-solving strategy. We used a modified version of the classic impossible task, in which the subjects simultaneously faced three possible and one impossible trials. Additionally, subjects were tested in four different conditions: social condition (with an unknown experimenter); asocial condition (subject alone); 'dummy' human condition (with a 'dummy' human); object condition (with a big sheet of cardboard). Finally, we compared two populations of dogs differing in their experience of receiving help from humans: 20 pet dogs tested in their houses and 31 free-ranging dogs tested in Morocco. We found that the pet dogs and free-ranging dogs had similar persistence in interacting with the impossible task in all conditions. Moreover, subjects looked back with similar latencies at the human, at the dummy human and at the object. Overall, pet dogs looked back longer at the human than free-ranging dogs. This could be interpreted as pet dogs being more attracted to humans and/or having a stronger association between humans and food than free-ranging dogs. Concluding, the looking back in an impossible task does not represent a problem-solving strategy. This behaviour seems rather linked to the subject's persistence, to the salience of the stimuli presented, and potentially to the past reinforcement history.

Importance of a species' socioecology: Wolves outperform dogs in a conspecific cooperation task.

A number of domestication hypotheses suggest that dogs have acquired a more tolerant temperament than wolves, promoting cooperative interactions with humans and conspecifics. This selection process has been proposed to resemble the one responsible for our own greater cooperative inclinations in comparison with our closest living relatives. However, the socioecology of wolves and dogs, with the former relying more heavily on cooperative activities, predicts that at least with conspecifics, wolves should cooperate better than dogs. Here we tested similarly raised wolves and dogs in a cooperative string-pulling task with conspecifics and found that wolves outperformed dogs, despite comparable levels of interest in the task. Whereas wolves coordinated their actions so as to simultaneously pull the rope ends, leading to success, dogs pulled the ropes in alternate moments, thereby never succeeding. Indeed in dog dyads it was also less likely that both members simultaneously engaged in other manipulative behaviors on the apparatus. Different conflict-management strategies are likely responsible for these results, with dogs' avoidance of potential competition over the apparatus constraining their capacity to coordinate actions. Wolves, in contrast, did not hesitate to manipulate the ropes simultaneously, and once cooperation was initiated, rapidly learned to coordinate in more complex conditions as well. Social dynamics (rank and affiliation) played a key role in success rates. Results call those domestication hypotheses that suggest dogs evolved greater cooperative inclinations into question, and rather support the idea that dogs' and wolves' different social ecologies played a role in affecting their capacity for conspecific cooperation and communication.

Dogs and wolves do not differ in their inhibitory control abilities in a non-social test battery.

Being able to inhibit certain behaviours is of clear advantage in various situations. In particular, it has been suggested that inhibitory control plays a role in problem-solving and cooperation. Interspecific differences in the capacity for inhibitory control have been attributed to social and ecological factors, while one additional factor, namely domestication, has received only little attention so far. Dogs are an interesting species to test the effects of socio-ecological factors and also the influence of domestication on inhibitory control abilities. While dogs might have been selected for enhanced inhibition skills during domestication, the predictions derived from their socio-ecological background are reversed. Wolves are cooperative hunters and breeders, while dogs predominately scavenge and raise their young alone, accordingly, it would be predicted that dogs show impaired inhibitory control abilities since they no longer rely on these coordinated actions. To test these hypotheses, we assessed inhibitory control abilities in dogs and wolves raised and kept under similar conditions. Moreover, considering the problem of context-specificity in inhibitory control measures, we employed a multiple-test-approach. In line with previous studies, we found that the single inhibition tests did not correlate with each other. Using an exploratory approach, we found three components that explained the variation of behaviours across tests: motivation, flexibility, and perseveration. Interestingly, these inhibition components did not differ between dogs and wolves, which contradicts the predictions based on their socio-ecological backgrounds but also suggests that at least in tasks with minimal human influence, domestication did not affect dogs' inhibitory control abilities, thus raising questions in regard to the selection processes that might have affected inhibitory control abilities during the course of domestication.

Analytical validation of an Enzyme Immunoassay for the measurement of urinary oxytocin in dogs and wolves.

Assessing changes in oxytocin (OT) levels in response to a variety of social stimuli has become of major interest in the field of behavioral endocrinology. OT is involved in the regulation of various aspects of social behavior such as tolerance, and the formation and maintenance of social bonds but also the regulation of stress. All of these aspects have been identified as potential targets of selection during the domestication process. Therefore, comparing the role of the oxytocinergic system in various aspects of dog and wolf social behavior, might help to understand whether this system was involved in the domestication process. Studies assessing OT levels in dogs and wolves have used invasively collected plasma and serum samples and non-invasively collected urine samples. However, when using an assay system on a new species a careful and complete validation of the method is of crucial importance, and to date no proper validation, to assess urinary OT levels in dogs and wolves, has been reported. We therefore conducted an analytical validation of an Enzyme Immunoassay (EIA) for the measurement of OT in urine of dogs and wolves, using a commercially available EIA. Stability tests revealed that OT levels degrade over time when stored at 4 °C, but are little affected by repeated thawing. In addition, our results indicate that the variance in OT levels is slightly lower when phosphoric acid is added following collection to prevent OT degradation. Long term storage tests revealed that urinary OT levels are least variable when stored as extracts in ethanol at -20 °C, rather than as unextracted urine samples. Validation results were acceptable with regard to parallelism, but values for accuracy and extraction efficiency were not meeting the standard criteria usually applied to steroid EIAs, especially when assessed for the lower range of the assay. The results of this study highlight the importance of an analytical assay validation, since even if validation parameters are not optimal, if published, they allow readers to estimate the relevance of studies using the validated method.

The effect of training and breed group on problem-solving behaviours in dogs.

Dogs have become the focus of cognitive studies looking at both their physical and social problem-solving abilities (Bensky et al. in Adv Stud Behav, 45:209-387, 2013), but very little is known about the environmental and inherited factors that may affect these abilities. In the current study, we presented a manipulation task (a puzzle box) and a spatial task (the detour) to 128 dogs belonging to four different breed groups: Herding, Mastiff-like, Working and Retrievers (von Holdt et al. in Nature 464:898-902, 2010). Within each group, we tested highly trained and non-trained dogs. Results showed that trained dogs were faster at obtaining the reward in the detour task. In the manipulation task, trained dogs approached the apparatus sooner in the first familiarization trial, but no effect of breed emerged on this variable. Furthermore, regardless of breed, dogs in the trained group spent proportionally more time interacting with the apparatus and were more likely to succeed in the test trial than dogs in the non-trained group, whereas regardless of training, dogs in the working breed group were more likely to succeed than dogs in the retriever and herding breed groups (but not the mastiff-like group). Finally, trained dogs were less likely to look at a person than non-trained dogs during testing, but dogs in the herding group more likely to do so than dogs in the retriever and working but not the mastiff-like breed groups. Overall, results reveal a strong influence of training experience but less consistent differences between breed groups on different components thought to affect problem solving.

Free-ranging dogs match a human's preference in a foraging task.

Social learning is a mechanism used by many species to efficiently gain information about their environment. Although many animals live in an environment where members of other species are present, little is known about interspecific social learning. Domesticated and urbanized species provide the opportunity to investigate whether nonhuman animals can learn from heterospecifics such as humans, who are integral parts of their social landscape. Although domestic dogs Canis familiaris have been intensively researched for their ability to learn from humans, most studies have focused on dogs living as pets. However, free-ranging dogs represent the majority of the world's dog population, they live alongside humans, scavenge on human refuse, and are subject to natural and sexual selection. Thus, free-ranging dogs with extensive exposure to humans and their artifacts provide the opportunity to investigate interspecific social learning in a naturalistic setting, where learning from humans might be a benefit for them. Here we tested individual free-ranging dogs in a between-subject design: Dogs in the control group could spontaneously choose between two novel and differently patterned food-delivering boxes. In the experimental group, instead, dogs could first observe an unfamiliar human approaching and eating from 1 of the 2 boxes. We provide the first evidence that free-ranging dogs match the choice of an unfamiliar human. These results show that at least simple forms of interspecific social learning might be involved in dogs' success in living alongside humans in a complex urbanized environment.

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.

Intra and interspecific audience effect on domestic dogs' behavioural displays and facial expressions.

The aim of the current study was to investigate the influence of both intra- and interspecific audiences on dogs' facial expressions and behaviours. Forty-six dogs were exposed to three test conditions in which a food reward, initially available, was denied when in the presence of either a human (Human condition) or a dog audience (Dog condition), or in the absence of a visible audience (Non-social condition). Salivary cortisol was collected to evaluate the stress/arousal activation in the different conditions. Compared to the Non-social condition, the presence of a conspecific evoked more facial expressions, according to the DogFACS (Facial Action Coding System, an anatomically based tool to analyze facial expressions in domestic dogs), (EAD105-Ears downward), displacement behaviours (AD137-Nose licking, AD37-Lip wiping), tail wagging, whining, and panting (AD126). When facing a conspecific, dogs assumed a more avoidant attitude, keeping a distance and not looking at the stimuli, compared to when in the presence of the human partner. Dogs also exhibited more facial expressions (EAD102-Ears Adductor, EAD104-Ears Rotator), displacement behaviours (AD137-Nose licking, AD37-Lip wiping), panting (AD126) and whining when facing the conspecific than the human partner. Post-test cortisol was not influenced by any condition, and no association between pre-test cortisol and behavioural variables was found, thus strong differences in the levels of stress/arousal were unlikely to be responsible for differences in behavior between conditions. Considering the current results in the context of the available literature, we suggest that the higher displacement behaviors exhibited with the conspecifics were likely due to an increased level of uncertainty regarding the situations.

Urbanization does not affect red foxes' interest in anthropogenic food, but increases their initial cautiousness.

Human presence and activities have profoundly altered animals' habitats, exposing them to greater risks but also providing new opportunities and resources. The animals' capacity to effectively navigate and strike a balance between risks and benefits is crucial for their survival in the Anthropocene era. Red foxes (Vulpes vulpes), adept urban dwellers, exhibit behavioral plasticity in human-altered environments. We investigated variations in detection frequency on trail cameras and the behavioral responses (explorative, bold, and fearful) of wild red foxes living along an urbanization gradient when exposed to a metal bin initially presented clean and then filled with anthropogenic food. All fox populations displayed an increased interest and similar explorative behavioral responses toward the anthropogenic food source, irrespective of the urbanization gradient. Despite no impact on explorative behaviors, foxes in more urbanized areas initially showed heightened fear toward the empty bin, indicating increased apprehension toward novel objects. However, this fear diminished over time, and in the presence of food, urban foxes displayed slightly reduced fear compared with their less urban counterparts. Our results highlight foxes' potential for adaptability to human landscapes, additionally underscoring the nuanced interplay of fear and explorative behavioral response of populations living along the urbanization gradient.

Village dogs match pet dogs in reading human facial expressions.

Most studies on dogs' cognitive skills in understanding human communication have been conducted on pet dogs, making them a role model for the species. However, pet dogs are just a minor and particular sample of the total dog world population, which would instead be better represented by free-ranging dogs. Since free-ranging dogs are still facing the selective forces of the domestication process, they indeed represent an important study subject to investigate the effect that such a process has had on dogs' behavior and cognition. Despite only a few studies on free-ranging dogs (specifically village dogs) having been conducted so far, the results are intriguing. In fact, village dogs seem to place a high value on social contact with humans and understand some aspects of humans' communication. In this study we aimed to investigate village dogs' ability in understanding a subtle human communicative cue: human facial expressions, and compared them with pet dogs, who have already provided evidence of this social skill. We tested whether subjects were able to distinguish between neutral, happy, and angry human facial expressions in a test mimicking a potential real-life situation, where the experimenter repeatedly performed one facial expression while eating some food, and ultimately dropped it on the ground. We found evidence that village dogs, as well as pet dogs, could distinguish between subtle human communicative cues, since they performed a higher frequency of aversive gazes (looking away) in the angry condition than in the happy condition. However, we did not find other behavioral effects of the different conditions, likely due to the low intensity of the emotional expression performed. We suggest that village dogs' ability in distinguishing between human facial expressions could provide them with an advantage in surviving in a human-dominated environment.

Similar behavioral but different endocrine responses to conspecific interactions in hand-raised wolves and dogs.

Domestication has altered dogs' conspecific social organization compared to their closest, non-domesticated relatives, gray wolves. Wolves live in packs whose survival depends on coordinated behavior, but dogs rely less on conspecifics, which predicts greater cohesiveness in wolf than dog packs. Endocrine correlates such as oxytocin and glucocorticoids modulate group cohesion resulting in species-specific differences in social interactions. We found that although wolves' and dogs' observable behavioral reactions to a territorial threat and separation from the pack were similar, hormonal responses differed. Wolves' but not dogs' oxytocin and glucocorticoid concentrations correlated positively with territorial behaviors and only wolves showed increased glucocorticoid concentrations after separation from their pack. Together, results suggest stronger emotional activation to threats to group integrity in wolves than dogs, in line with their socio-ecology.

Comparing wolves and dogs: current status and implications for human 'self-domestication'.

Based on claims that dogs are less aggressive and show more sophisticated socio-cognitive skills compared with wolves, dog domestication has been invoked to support the idea that humans underwent a similar 'self-domestication' process. Here, we review studies on wolf-dog differences and conclude that results do not support such claims: dogs do not show increased socio-cognitive skills and they are not less aggressive than wolves. Rather, compared with wolves, dogs seek to avoid conflicts, specifically with higher ranking conspecifics and humans, and might have an increased inclination to follow rules, making them amenable social partners. These conclusions challenge the suitability of dog domestication as a model for human social evolution and suggest that dogs need to be acknowledged as animals adapted to a specific socio-ecological niche as well as being shaped by human selection for specific traits.

Wolves and dogs fail to form reputations of humans after indirect and direct experience in a food-giving situation.

Reputation is a key component in social interactions of group-living animals and appears to play a role in the establishment of cooperation. Animals can form reputations of individuals by directly interacting with them or by observing them interact with a third party, i.e., eavesdropping. Previous research has focused on whether dogs (Canis lupus familiaris) can eavesdrop on humans because of their ability to cooperate with humans, however the results are mixed and if they can eavesdrop, it is unknown whether this ability evolved during the domestication process or whether it was inherited from their ancestor, wolves (Canis lupus). Our study investigated whether equally hand-raised, pack-living dogs and wolves can form reputations of humans in a food-giving situation through indirect and/or direct experience. The experimental procedure comprised three parts: baseline (to test whether the subject preferred a person prior to the experiment), observation and testing. In the observation phase, the subject observed two humans interact with a dog demonstrator-one acted generously and fed the dog, and the other acted selfishly and refused to feed the dog. The subject could then choose which person to approach in the test phase. In the following experience phase, the animals interacted directly with the same two humans who behaved either in a generous or selfish manner. Then, they were again given a choice whom to approach. We found that dogs and wolves, at the group level, did not differentiate between a generous or selfish partner after indirect or direct experience, but wolves were more attentive towards the generous person during the observation phase and some dogs and wolves did prefer the generous partner, at least after indirect and direct experience was combined. Our study suggests that reputation formation may be more difficult than expected for animals and we emphasise the importance of context when studying reputation formation in animals.

Audience effect on domestic dogs' behavioural displays and facial expressions.

In the present study we investigated the influence of positive and negative arousal situations and the presence of an audience on dogs' behavioural displays and facial expressions. We exposed dogs to positive anticipation, non-social frustration and social frustration evoking test sessions and measured pre and post-test salivary cortisol concentrations. Cortisol concentration did not increase during the tests and there was no difference in pre or post-test concentrations in the different test conditions, excluding a different level of arousal. Displacement behaviours of "looking away" and "sniffing the environment" occurred more in the frustration-evoking situations compared to the positive anticipation and were correlated with cortisol concentrations. "Ears forward" occurred more in the positive anticipation condition compared to the frustration-evoking conditions, was positively influenced by the presence of an audience, and negatively correlated to the pre-test cortisol concentrations, suggesting it may be a good indicator of dogs' level of attention. "Ears flattener", "blink", "nose lick", "tail wagging" and "whining" were associated with the presence of an audience but were not correlated to cortisol concentrations, suggesting a communicative component of these visual displays. These findings are a first step to systematically test which subtle cues could be considered communicative signals in domestic dogs.

Artificially elevated oxytocin concentrations in pet dogs are associated with higher proximity-maintenance and gazing towards the owners.

The relationship between dogs and their owners is characterized by an affective and enduring bond. It has been suggested that oxytocin might be the underlying mechanism driving this relationship, however evidence is mixed. In this study we tested whether intranasally administered oxytocin (compared to saline) would influence dogs' behavioural synchrony and shared attention towards their owners. Each individuals' pre and post administration oxytocin concentrations (measured in urine) were included in the analyses. Urinary oxytocin concentrations after administrations were positively associated with dogs' duration of social proximity and looking behaviours towards their owners supporting the role of oxytocin in modulating dogs' human-directed social behaviours.

Life experience rather than domestication accounts for dogs' increased oxytocin release during social contact with humans.

Dogs' increased human-directed sociability compared to wolves may be the result of increased oxytocin system activity and decreased stress responses, but comparative studies accounting for life experience are lacking. We compared hand-raised, pack-living wolves' and dogs' behavior and hormone concentrations after interacting with a closely bonded and a familiar human. Both preferred the bonded partner, but dogs showed less variability in human-directed sociability than wolves. Physical contact was not associated with oxytocin but correlated positively with glucocorticoids in the pack-living animals when the human was not bonded. To clarify the role of life experience, we tested pet dogs and found that oxytocin concentrations correlated positively with physical contact with their owners, while glucocorticoids remained unaffected. Results show that, given similar experiences, wolf-dog differences in human-directed sociability and associated hormones are subtle and indicate that factors related to life as a pet dog rather than domestication account for oxytocin release during human-dog interactions.

Validation of a commercial enzyme immunoassay to assess urinary oxytocin in humans.

Within the last decade, oxytocin (OT) has attracted a lot of attention in the context of various human social behaviors. Besides its importance in regulating physiological processes in females related to giving birth and lactation, OT is involved in the establishment and maintenance of social relationships, trust and emotion recognition. However, results are not always consistent across studies, which may partly be due to the incomplete validation of methods used to assess OT levels. Carefully validating a method before its use is of crucial importance to ensure that it can be used to accurately, reliably and repeatedly assess OT levels. With this study we evaluated a commercially available Enzyme Immunoassay to assess OT in human urine samples by conducting a careful analytical validation. Results indicate that, with regard to parallelism and immunoreactivity, human urinary OT can be assessed reliably. However, extraction methods need further improvement to optimize measures of accuracy and extraction efficiency, especially in the lower range of the assay system. Tests on OT stability indicate that OT is affected by degradation when stored at 4°C or room temperature. Storing urine samples over longer periods revealed that OT levels are most stable when stored as ethanol extracts at -20°C compared to being stored as samples at -20°C or -80°C. Although some of the validated parameters did not reach the intended quality criteria, this study highlights the importance of such in depth validation procedures and reporting results to make them available to researchers embarking on projects utilizing such methods.

Do dogs eavesdrop on human interactions in a helping situation?

Eavesdropping is the acquisition of information by observing third-party interactions. Considering dogs' (Canis lupus familiaris) dependence on humans, it would be beneficial for them to eavesdrop on human interactions to choose an appropriate partner to associate with. Previous studies have found that dogs preferred a human who acted generously or cooperatively towards another human over one who acted selfishly or non-cooperatively, however they often did not control for potential location biases. This study controlled for local enhancement and investigated whether dogs derive and act on information about unfamiliar humans through reputation-like inferences by observing third-party interactions. 42 dogs participated in the experiment, which consisted of an observation phase and a test phase. In the observation phase, the animals observed a human with a box of food ask for help to open it from two people-one was helpful and the other was not. The test phase consisted of the impossible task and a choice test. Half of the sample was tested in the experimental condition and the other half was tested in the side control condition, where the two people swapped positions before the test phase. The results of the impossible task showed that dogs only looked at the helpful person first when the people stayed on the same side as they did in the observation phase. In the choice test, dogs chose at random, regardless of whether the people stayed on the same side or swapped positions. Our findings provide tentative support for a local enhancement interpretation of eavesdropping.

What matters for cooperation? The importance of social relationship over cognition.

Cooperation is vital for the survival of many species and has been extensively researched at the ultimate level however, there is a considerable degree of variation within a given species in the extent of cooperative behaviours exhibited. Possible factors that have been discussed to contribute to this variation are the social relationship between the cooperating individuals, but also non-social factors such as inhibitory control. Investigating the performance of wolves, a highly cooperative species, in three experimental cooperative tasks; a coordination (string-pulling) task, a prosocial task and an inequity aversion task, we found that the social relationship between the partners had the largest effects on all tasks, while non-social factors (inhibition, learning speed, causal understanding and persistence) had rather unpredicted, or no effects. The results support the potential importance of relational factors, rather than motivation and cognitive abilities, in driving cooperative interactions.