Association Behavior Research Articles

Dopamine-mediated behavioral alterations following exposure to a social video in socially isolated mice during the developmental period.

Video exposure is known to affect brain function, yet its impact on neurodevelopmental processes remains unclear. This study aimed to investigate whether exposure to a video depicting social behavior induces behavioral and neurological changes in socially isolated mice. On Postnatal Day (PND) 21, male mice were separated from their dams and randomly assigned to three groups: socially grouped mice; socially isolated mice (ISO), where mice were housed without any social stimulation; and social video-exposed mice (SVE), where mice were exposed to a social video played on a tablet from PND21 to PND56 under socially isolated conditions. On PND56, all animals underwent behavioral tests. Compared to the socially grouped mice and ISO group, the SVE group showed an attenuated response to amphetamine treatment. In the social cognition test, the ISO group exhibited decreased affiliative behavior and increased offensive and defensive behavior. However, the SVE group showed a partial improvement in social cognition, including increased affiliative behaviors and decreased defensive behaviors, although no changes in offensive behaviors were observed. Furthermore, the SVE group exhibited elevated levels of tyrosine hydroxylase and dopamine transporter in key social cognition regions-namely the prefrontal cortex, retrosplenial cortex, and hippocampus. This neurochemical shift implies that socially isolated mice can acquire social behaviors through exposure to video-based social interactions. These effects may be related to the compensatory response of the dopamine system, which is implicated in various psychiatric disorders. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Effects of short-term isolation on social behaviors in prairie voles.

Social isolation affects the brain and behavior in a variety of animals, including humans. Studies in traditional laboratory rodents, including mice and rats, have supported the idea that short-term social isolation promotes affiliative social behaviors, while long-term isolation promotes anti-social behaviors, including increased aggression. Whether the effects of isolation on the social behaviors of mice and rats generalize to other rodents remains understudied. In the current study, we characterized the effects of short-term (3-days) social isolation on the social behaviors of adult prairie voles (Microtus ochrogaster) during same-sex and opposite-sex social interactions. Our experiments revealed that short-term isolation did not affect rates of ultrasonic vocalizations or time spent in non-aggressive social behaviors and huddling during same-sex and opposite-sex interactions. Unexpectedly, although short-term isolation also did not affect time spent in resident-initiated and mutually-initiated aggressive behavior, we found that short-term isolation increased time spent in visitor-initiated aggression during male-male interactions. Our findings highlight the importance of comparative work across species and the consideration of social context to understand the diverse ways in which social isolation can impact social behavior.

Improving Reproductive Success in Captive Marmosets Through Active Female Choice.

The recent upsurge in the use of common marmosets (Callithrix jacchus) as a desirable model for high-priority biomedical research has challenged local and global suppliers struggling to provide sufficient numbers of marmosets for large-scale projects. In laboratories, random male-female pairings are often unsuccessful, with intervals of several months before attempting alternate pairings. Here we address this challenge through a behavioral task that promotes self-directed female selection of potential mates to increase the efficiency of breeding in captive marmosets. We created a partner preference test in which nulliparous females (n = 12) had the opportunity to select between two eligible males (n = 23) at a time, in a forced choice test. In this test, both males and females displayed sexual solicitations. However, the females displayed a clear preference for one male by directing affiliative behaviors toward him including proceptive tongue-flicking, approach, and grooming. Her preference remained consistent across three consecutive test sessions. This method resulted in a 2.5-fold improvement in breeding success within 90 days compared to random pairings. This cost-effective and straightforward pairing practice can be used to enhance breeding efficiency in both small and large marmoset colonies.

The Effects of the Fire Hose Square Knot Browser as a Foraging Enrichment Device on the Behavior of Captive Macaca fascicularis.

Effective management of captive M. fascicularis (long-tailed macaques) is crucial for maintaining high-quality research models, necessitating strategies to promote their welfare. This study evaluated the impact of a foraging enrichment device, the "fire hose square knot browser", on the behavior of 32 long-tailed macaques at the Primate Research Center of IPB University in Bogor, Indonesia. We observed and analyzed daily behaviors across various food types over 288 h using scan and instantaneous sampling methods. Statistical analyses, including ANOVA and Kruskal-Wallis tests, revealed significant behavioral changes in the presence of the foraging enrichment device. The foraging enrichment device notably increased eating and affiliative behaviors, while reducing resting, agonistic, and stereotypic behaviors. No significant differences in eating, auto-grooming, resting, sexual, agonistic, or stereotypic behaviors were observed between the morning and afternoon. However, mobility and affiliation behaviors varied between these periods. The highest percentage of eating behavior occurred with the enrichment foraging device and a mixture of fruits. Furthermore, a three-way non-parametric analysis suggests a significant effect of food type and treatment on behaviors such as mobility and stereotyping. These findings underscore the positive impact of foraging enrichment devices on promoting active behavior and enhancing animal welfare in captive long-tailed macaques.

Behavioral inhibition and social maladjustment: The moderation role of social behaviors during cooperative and competitive peer interactions.

Behavioral inhibition (BI) is a temperamental characterized in early childhood by intense wariness and negative affect toward novelty, and is linked to children's emotional symptoms and peer problems. How children behave or respond toward diverse social contexts can influence the relation between BI and social adjustment. This study investigated the effect of children's affiliative and antagonistic behavior in cooperative and competitive contexts on the relation between early BI and social adjustment using a longitudinal design. Children's BI (at age 2) was assessed via laboratory observations. Affiliative and antagonistic behaviors (at age 4) were coded during a dyadic truck game in the cooperative and competitive contexts. Children's emotional symptoms and peer problems (at age 4) were assessed using parental reports. These results suggest that high affiliative behavior in the cooperative context was linked to a reduced level of peer problems in inhibited children. Interestingly, highly antagonistic behavior in the competitive context was linked to a reduced level of emotional symptoms in inhibited children. These findings extend our understanding of the role social behavior plays in the social adjustment of behaviorally inhibited children by highlighting the contribution of socially appropriate behaviors in social contexts. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Mu opioid receptor expression by nucleus accumbens inhibitory interneurons promotes affiliative social behavior.

Mu opioid receptors in the nucleus accumbens regulate motivated behavior, including pursuit of natural rewards like social interaction as well as exogenous opioids. We used a suite of genetic and viral strategies to conditionally delete mu opioid receptor expression from all major neuron types in the nucleus accumbens. We pinpoint inhibitory interneurons as an essential site of mu opioid receptor expression for typical social behavior, independent from exogenous opioid sensitivity.

Third‐Party Affiliation in Domestic Dogs During and After a Human Conflict

ABSTRACTSeveral behaviors occur in the aftermath of within‐group conflicts. These include spontaneous affiliation toward the victim from an uninvolved third party. When third‐party affiliations reduce the stress of the victim, this behavior has been defined as consolation. Given the absence of previous reports, the objective of the present study was to evaluate the presence of third‐party post‐conflict affiliation when dogs (Canis lupus familiaris) observe their owners arguing. We carried out two studies varying the intensity and the duration of the dispute. Affiliative behaviors toward each of the owners were registered, as well as stress‐related behaviors. Our findings support the existence of third‐party affiliation from dogs toward their owners during and after a conflict between them, evidenced as higher rates of victim‐directed affiliative behaviors in the experimental condition versus the control, in both studies. Moreover, dogs exhibited more stress‐related behaviors in the experimental condition compared to the control, but only in the second study, which suggests these stimuli were experienced as aversive, even though they were not aimed at the dogs. In addition, in the second study dogs displayed aggressor‐directed behaviors that could be interpreted as appeasement. Finally, there was no evidence that the level of the bond between the dog and each owner acts as a modulator of affiliative behavior. Further studies are required to expand our understanding of these abilities of dogs and its effects on the emotional state of the victim.

Spitz-like tail carriage in two domestic cats

Domestic cats use visual cues to communicate with conspecifics and humans. This includes the position and movement of the tail. The tail up signal (i.e. tail held vertically with the tip curled) has been identified as a friendly greeting signal between cats and from cats to humans. We present here a report of two cats unable to display the classic tail up signal due to Spitz-like (curled) tail characteristics, a morphology not previously reported in the scientific literature. The cats, a British Shorthair (Mn, 2 y) and Domestic Longhair (Fn, 8.5 y), belonged to different households and were participants in a study of intraspecific social interactions. Video recordings show the cats displaying normal tail movements (waving, swishing, twitching) and position when the tail was hanging down. However, once the tail was raised to a vertical position, it immediately curled over the back. This Spitz-like tail posture was displayed both when greeting people and other cats. It had reportedly been present since adoption. There was no underlying medical history of injury or pain to indicate this was an acquired state. We suggest this Spitz-like tail is a spontaneously occurring anomaly, that does not seem to noticeably impair the cats’ communicative abilities, as normal affiliative behaviours were observed during interactions with the cohoused cat. We discuss the significance of this finding in relation to the formation of social bonds and the signalling of affiliative intent.

Social networks of pregnant gilts during outdoor feeding and the effects on their offspring

Social relationships are important aspects of the behavioural biology of pigs and can be affected by the type of housing pigs are kept in. Exploring agonistic interactions and affiliative behaviours can reveal effects on adult pigs and their descendants. This research investigated the social dynamics among gilts throughout pregnancy during collective feeding in an outdoor housing system and the effects of these dynamics on the stability of the group and the offspring of the group members. For this study, 15 gilts were oestrus synchronised and artificially inseminated with three different semen pools. The paddocks where the gilts were housed contained a mud pool, natural tree shade, and two nipple drinkers. Two daily meals (∼2.5 kg/day/gilt) were provided to the group on the floor. Feeding behaviour was recorded for three continuous days (20 min in the morning and again in the afternoon) every gestational (a total of 42 h of video recording). Saliva samples were collected at 6:00 a.m. and 6:00 p.m. on these same days. A trained observer evaluated all the videos using Boris software to determine agonistic and affiliative behaviours. After farrowing, the piglet data collected included sex, mortality, and body weight (BW) at 10, 25, 29, and 36 d of age. Elo scores were calculated to quantify the relative hierarchy among the gilts based on the behaviour assessment. Generalised linear mixed models (GLMMs) were used for data analyses, and the significance of fixed effects was determined at p < 0.05. The tendency of the gilts to feed together decreased as gestation progressed. Heavier gilts had lower salivary cortisol concentrations, and higher gilt rank was correlated with higher morning salivary cortisol concentrations and heavier piglets. Maternal modulation of offspring performance in pigs warrant further investigation. Assessment of gilts' social feeding behaviours is relevant for considering pigs' behaviour in genetic selection and improving commercial facilities and management practices to improve animal welfare.

Patterns of Conflict and Post-Conflict Affiliation in Propithecus diadema and Eulemur fulvus

AbstractGroup-living in primates provides benefits but also entails competition and aggression. To retain the positive fitness-enhancing advantages of social bonding, individuals can reconcile past aggression. Reconciliation has been extensively studied in haplorrhine primates and occurs more frequently in more tolerant species, but whether this pattern extends to strepsirrhine primates, including lemurs, remains unclear, particularly given the differences in behavioral biology between the two primate suborders. We examined the occurrence of reconciliation behavior and its relationship with dominance hierarchy characteristics in wild populations of Propithecus diadema and Eulemur fulvus. We collected behavioral data on dominance and affiliation behaviors in the Maromizaha Protected Area, Madagascar, focusing on three P. diadema groups and two E. fulvus groups over 14 months between 2015 and 2020. The dominance hierarchies differed between species, with P. diadema exhibiting steeper within-group hierarchies than E. fulvus. We found evidence of reconciliation behavior in P. diadema, as affiliation was more likely to follow conflicts than during control periods, but we did not find this effect in E. fulvus. Furthermore, reconciliation tendencies in P. diadema were higher in male–male dyads and those with disparate ranks. These findings suggest that dominance hierarchy structure may be an important factor influencing reconciliation behavior across primates, although the nuances of the relationship seem to vary between our two strepsirrhine study species and traditional haplorrhine patterns. Further research is needed to determine whether these patterns are species-, site-, or group-specific. In conclusion, these results further our understanding of the differences between strepsirrhine and haplorrhine social evolution.

Oxytocin effects on socially transmitted food preferences are moderated by familiarity between rats.

In the socially transmitted food preference (STFP) paradigm, rats change their preference for food rewards after socially interacting with a conspecific who has been fed with the originally non-preferred food. Here, we asked if oxytocin (OXT), a neuropeptide known for its role in social affiliation and social behavior, plays a role in STFP. Since OXT's influences on social behavior can be familiarity-dependent, we further asked if OXT effects on STFP are moderated by the familiarity between rats. Does OXT modulate rats' socially transmitted food choices in a familiarity-dependent way. We systemically injected either vehicle, low-dose (0.25mg/kg) of OXT, or large-dose (1.0mg/kg) of OXT before social interaction with either a familiar cagemate (in-group) or an unfamiliar conspecific from a different cage (out-group). We found an intergroup bias in STFP: vehicle-treated rats showed larger socially transmitted changes in food preference in the out-group than the in-group condition. OXT modulated STFP in a familiarity-dependent way: OXT prevented the increase in the consumption of the non-preferred food in the out-group, and decreased the consumption of the preferred food in the in-group. These effects were dose-dependent and observed under acute OXT action, but also on the subsequent day when acute OXT effects dissipated, suggesting long-lasting social learning effects of OXT. Additional analyses suggest that the familiarity and dose-dependent effects of OXT on STFP cannot be attributed to OXT's anorexic actions or differences in the duration of the social interactions. OXT modulates STFP in a familiarity-dependent way.

Serotonin drives aggression and social behaviors of laboratory male mice in a semi-natural environment.

Aggression is an adaptive social behavior crucial for the stability and prosperity of social groups. When uncontrolled, aggression leads to pathological violence that disrupts group structure and individual wellbeing. The comorbidity of uncontrolled aggression across different psychopathologies makes it a potential endophenotype of mental disorders with the same neurobiological substrates. Serotonin plays a critical role in regulating impulsive and aggressive behaviors. Mice lacking in brain serotonin, due to the ablation of tryptophan hydroxylase 2 (TPH2), the rate-limiting enzyme in serotonin synthesis, could serve as a potential model for studying pathological aggression. Home cage monitoring allows for the continuous observation and quantification of social and non-social behaviors in group-housed, freely-moving mice. Using an ethological approach, we investigated the impact of central serotonin ablation on the everyday expression of social and non-social behaviors and their correlations in undisturbed, group-living Tph2-deficient and wildtype mice. By training a machine learning algorithm on behavioral time series, "allogrooming", "struggling at feeder", and "eating" emerged as key behaviors dissociating one genotype from the other. Although Tph2-deficient mice exhibited characteristics of pathological aggression and reduced communication compared to wildtype animals, they still demonstrated affiliative huddle behaviors to normal levels. Altogether, such a distinct and dynamic phenotype of Tph2-deficient mice influenced the group's structure and the subsequent development of its hierarchical organization. These aspects were analyzed using social network analysis and the Glicko rating methods. This study demonstrates the importance of the ethological approach for understanding the global impact of pathological aggression on various aspects of life, both at the individual and group levels. Home cage monitoring allows the observation of the natural behaviors of mice in a semi-natural habitat, providing an accurate representation of real-world phenomena and pathological mechanisms. The results of this study provide insights into the neurobiological substrate of pathological aggression and its potential role in complex brain disorders.

Temperament of the dairy cow relates to her maternal behaviour in a pasture-based extended suckling system

Cow-calf rearing is gaining interest in dairy systems as an alternative to calf separation soon after birth. One commonly articulated benefit of these ‘extended suckling’ systems is that they allow expression of highly motivated maternal behaviours. The quality of maternal expression is subject to natural variation, however, and could be influenced by the temperamental characteristics of the dam. This study assessed the relationship between cow temperamental characteristics and expression of maternal behaviours in a pasture-based extended suckling system. Sixteen dairy cows (Bos taurus) underwent social isolation, novel object and novel human tests at 4 months of pregnancy. A principal components analysis (PCA) was used to determine associations between cow responses in these tests. After parturition, the cows entered an extended suckling system (half-day contact) until calves were weaned. Cow-calf interactions at pasture were video recorded for 4 consecutive hours (∼09:00 AM – 1:00 PM) at weeks 3, 6 and 9 post-partum. These data were used to calculate a maternal behaviour score for cows by subtracting the frequency of “negative” maternal behaviours (i.e., agonistic behaviour delivered to own calf, rejecting own calf suckling attempt and rejecting attempted contact by own calf) from the frequency of “positive” maternal behaviours (i.e., nursing own calf, affiliative behaviour delivered to own calf and proximity to own calf). A Pearson correlation was then used to assess the relationship between factors scores and maternal scores. Three behavioural traits were identified from the PCA: boldness, anxiety and sociability. In general, cows delivered more affiliative behaviour to their calves than to other calves and to cows and nursed their own calf more than other calves. The maternal behaviour score varied (mean ± SD, 33 ± 13.4, minimum = 9, maximum = 49). Cows with higher loadings for boldness had a lower maternal behaviour score (p < 0.05). There was no correlation between maternal behaviour score and anxiety or sociability (p > 0.05). The lower maternal behaviour score of bold cows in this study might be influenced by their prioritisation of foraging and exploration over interactions with their calves. Despite the long-standing practice of calf separation soon after birth, the current study demonstrates that maternal abilities of pasture-based dairy dams persist. We conclude that cow temperamental characteristics are related to how the cows interacted with their calves.

Under the influence: exogenous testosterone influences men's cross-sex perceptions of sexual interest.

The sexual misperception bias is a cognitive bias in which men tend to overestimate sexual interest from women, potentially shaped by evolutionary mating strategies. Testosterone, often linked to mating behaviors, might play a role in sustaining sexual overperceptions. To explore this possibility, we conducted a placebo-controlled study with 190 heterosexual men, administering either 11 mg of testosterone or a placebo. Participants interacted with an attractive female confederate, while naïve raters assessed the confederate's affiliative behaviors. Our findings suggest that exogenous testosterone did not broadly impact sexual overperception. However, we found that affiliative behavior from the confederate was positively correlated with perceived sexual interest among testosterone-treated, but not placebo-treated men. In addition, we found that this effect among testosterone-treated men was contingent on their self-perceived attractiveness. Specifically, the confederate's affiliative behaviors were positively correlated with perceived sexual interest, but only for testosterone-treated men with average or above average self-perceived attractiveness. Furthermore, our data revealed that men's tendency to project their own short-term and long-term mating interests increases as a function of self-perceived attractiveness, and this coupling is enhanced by testosterone for long-term interest. Taken together, these results suggest that testosterone may potentiate existing biases, particularly when sexual motivation is high, and bias perceptions of friendly behavior when engaging in cross-sex mindreading. This study adds to the understanding of the neuroendocrine bases of social cognition, suggesting that testosterone can affect men's perceptions of potential mates.

Effects of a Brief Separation From the Owner While in the Home Environment: Comparison of Fearful and Control Dogs

ABSTRACT Separation from their owner is stressful for some dogs. Studies examining this phenomenon are usually carried out in novel places. However, given that separation distress can also impact the behavior and welfare of dogs in their home environment, it is critical to study them in this context as well. Our first aim was to evaluate the reactions of dogs to a brief separation from their owner in the home. Secondly, we aimed to examine differences in the reactions of dogs classified as fearful, without (n = 27) and with (n = 17) aggressive responses, as well as controls (n = 28). All dogs were adults, from various breeds and mixes, and lived as pets. Each dog’s behavior was evaluated across three phases: (1) 2 min interaction with owner (baseline), (2) 3 min separation from the owner (alone), and (3) 2 min after the owner returned (owner return). We measured exploration as well as affiliative and stress behaviors. The results show that dogs explored the environment more in phase 1, directed more behaviors toward the door through which the owner had left in phase 2, followed the owner leaving at the end of phase 2, and greeted them when they returned in phase 3. Dogs also spent more time near the owner after their absence in phase 3 than in phase 1. A decrease in exploration triggered by the absence of the owner in phase 2 and a lack of full exploration recovery in phase 3 were observed as possible indicators of stress. No differences were found between fearful dogs and controls. The results indicate that it is possible to evaluate dogs’ reactions to separation from their owner in a more naturalistic context. This could aid in the development of strategies to improve separation-related problems in dogs and thus improve their welfare and quality of life.

Sex-Specific Impacts of Early Life Sleep Disruption: Ethanol Seeking, Social Interaction, and Anxiety Are Differentially Altered in Adolescent Prairie Voles.

Early life sleep is important for neuronal development. Using the highly social prairie vole rodent model, we have previously reported that early life sleep disruption (ELSD) during the preweaning period results in interference with social bonding and increases ethanol consumption following a stressor in adulthood. Furthermore, ELSD increases parvalbumin expression and reduces glutamatergic neurotransmission in cortical regions in adult prairie voles. To understand the impact of ELSD on the lifespan, an examination of an earlier time in life is necessary. The aim of the present study was to examine behavioral outcomes of ELSD on adolescent prairie voles. Given the known effects of ELSD on development of neuronal systems involved in mood and social motivation, we hypothesized that anxiety, risk, and reward-related behaviors would be impacted by ELSD in adolescent prairie voles. We report that both male and female adolescent prairie voles that experienced ELSD showed heightened anxiety-like behavior compared to age-matched controls (CONs) as measured by a light-dark box. Additionally, both male and female ELSD voles showed reductions in both ethanol preference and consumption, and affiliative behavior compared to CONs. These results suggest that adolescent prairie voles of both sexes experience heightened anxiety-like behavior and reduced reward-seeking behaviors after ELSD. These results further suggest that early life sleep is critically important for neurotypical behaviors in adolescence.

Increased alertness and moderate ingroup cohesion in bonobos' response to outgroup cues.

In a number of species, including humans, perceived outgroup threat can promote ingroup cohesion. However, the distribution and selection history of this association across species with varied intergroup relations remains unclear. Using a sample of 8 captive groups (N = 43 individuals), we here tested whether bonobos, like chimpanzees, show more affiliative ingroup behaviour following perception of outgroup cues (unfamiliar male long-distance vocalisations). We used comparable methods to our previous study of captive chimpanzees, and found that, although weaker, there was an association for more frequent social grooming in response to the outgroup condition than the control condition, alongside more alert posture and increased self-directed behaviour. This provides preliminary evidence for an ancestral origin to the proximate association between outgroup cues and ingroup cohesion, at least prior to the Pan-Homo split, and suggests the presence of intergroup competition in our last common ancestor.

Cross-seasonal and diurnal variation in physical contact between sub-adult pigs

Social touch is an important aspect of social relationships and has a major influence on development and health. However, in many species the occurrence and function of social touch is unknown. Pigs have frequent physical contact but this behaviour is largely unexplored. The aim of this study was to investigate the undisturbed variation in physical contact between pigs, and to assess diurnal and seasonal influences. A stable group of ten Puławska sub-adult female pigs was observed for 406 h across four seasons during the day and night, by continuous observations on an individual level (406 h / pig). They were housed indoors (112 m2 pen) on straw bedding. The ethogram distinguished the amount of surface contact between pigs when lying, the orientation to others, social nosing, other non-agonistic social behaviour and agonistic behaviours. Resting location within the pen was recorded 48 times per pig, and dominance relationships were calculated from agonistic interactions. Data were analysed with mixed models accounting for repeated observations. Pigs spent on average 40 % of their time lying in body contact, most often lying with their extremities in contact (71 %), followed by lying in partial body contact (16 %) or full body contact (13 %) and were frequently nosing the head and body of others. The duration of lying in any type of contact, as well as agonistic behaviour, was influenced by season, with the longest durations in autumn. In summer, the duration of partial body contact was lowest, but full body contact was unaffected by season. Nosing behaviour remained constant throughout the year. Pigs lay in contact more during the night, while showing more social behaviours during the day. Pigs mostly lay in nonparallel orientation or head-to-head, but clearly least in the head-to-tail orientation. Season influenced the frequency of lying head-to-head and head-to-tail, but not lying nonparallel. The coefficient of variation of the lying location was influenced by season. Allo-grooming, mounting, and nudging were shown infrequently and mostly by specific individuals. In conclusion, when at a large space allowance, pigs spend nearly half of their time in body contact, even during the higher temperatures in summer. This shows that social touch, including affiliative behaviour, has an important role in pigs’ social life, and remains largely unaffected by external influences.

Affective Implications of Human-Animal Relationship on Pig Welfare: Integrating Non-Linear Heart Rate Variability Measures.

The human-animal relationship is crucial for animal welfare. Gentle handling enhances pigs' comfort while rough handling causes fear and stress. This study examined how different human-animal relationship qualities affect the behavior and heart rate variability (linear and non-linear parameters) of 36 nursery pigs. Over six weeks, pigs experienced positive (n = 12), minimal (n = 12), or negative (n = 12) human handling. Their responses to handlers were then assessed in an experimental arena with four phases: habituation, exposure to the handler standing and sitting, and forced interaction. Pigs subjected to negative handling exhibited increased fear-related behaviors, spending less time in contact with the handler. They also exhibited heightened stress responses, with greater LF/HF ratio and Lmean values compared with positively handled pigs. Conversely, gently handled pigs displayed affiliative behaviors, accepting more strokes, and higher parasympathetic activation, indicated by greater RMSSD/SDNN and SampEn values, suggesting a more positive affective state. Minimally handled pigs exhibited some behavioral similarities to gently handled pigs, although physiological data indicated that the interaction was likely more rewarding for the gently handled pigs. These results emphasize the impact of human-animal relationships on pig welfare and highlight the value of incorporating non-linear heart rate variability parameters in such evaluations.

Free-ranging dogs quickly learn to recognize a rewarding person

Individual human recognition is important for species that live in close proximity to humans. Numerous studies on domesticated species and urban-adapted birds have highlighted this ability. One such species which is heavily reliant on humans is the free-ranging dog. Very little knowledge exists on the amount of time taken by free-ranging dogs to learn and remember individual humans. Due to their territorial nature, they have a high probability of encountering the same people multiple times on the streets. Being able to distinguish individual humans might be helpful in making decisions regarding people from whom to beg for food or social reward. We investigated if free-ranging dogs are capable of identifying the person rewarding them and the amount of time required for them to learn it. We conducted field trials on randomly selected adult free-ranging dogs in West Bengal, India. On Day 1, a choice test was conducted. The experimenter chosen did not provide reward while the other experimenter provided a piece of boiled chicken followed by petting. The person giving reward on Day 1 served as the correct choice on four subsequent days of training. Day 6 was the test day when none of the experimenters had a reward. We analyzed the choice made by the dogs, the time taken to approach during the choice tests, and the socialization index, which was calculated based on the intensity of affiliative behaviour shown towards the experimenters. The dogs made correct choices at a significantly higher rate on the fifth and sixth days, as compared to Day 2, suggesting learning. This is the first study aiming to understand the time taken for individual human recognition in free-ranging dogs, and can serve as the scaffold for future studies to understand the dog-human relationship in open environments, like urban ecosystems.