Animal play and animal welfare

Physical Enrichment Enhances Growth in Artificially Reared Lambs

Precocious weaning is a common practise in large-scale sheep-dairy farming, despite causing distress and growth checks in lambs. We asked whether provision of physical enrichment objects would guard against growth checks during dairy lambs' first week in an artificial rearing system - arguably the most stressful period for artificially reared lambs. East Friesian Lacaune dairy ewe lambs aged approximately four to seven days were assigned to an Enrichment condition (N = 27) in which an object in the pen was changed daily, or a Control condition (N = 27) in which no object was available. Feeding and housing conditions were identical for both conditions. Lambs in the Enrichment condition experienced greater average daily weight gains (m = .33 kg; SD = .09) than Control-condition lambs (m = .21 kg; SD = .09) over the first week in the artificial rearing system (BF10 = 3071.15). Thus, provision of physical enrichment may be particularly beneficial for lambs following precocious weaning.

Towards a scientific definition of animal emotions: Integrating innate, appraisal, and network mechanisms

This paper introduces a mechanistic framework for understanding animal emotions, which is designed for biologists studying animal behavior and welfare. Researchers often examine emotions-short-term valenced experiences-through behavioral, somatic, and cognitive indicators. However, proposed indicators are often ambivalent (emerge in contexts with opposing emotional valence) or undetermined (arise in both affective and non-affective processes). To ground hypothesis formulation regarding animal emotions on a better foundation, the paper advocates for building on what we know regarding the mechanisms of human emotions-the behavioral rules that transform sensory input into motor output during emotional episodes. In particular, it integrates key assumptions from three dominant psychological theories of emotion-innate, appraisal, and network theories-into a single framework and argues that this can serve as a common ground to transfer insights from human to animal emotion research. Additionally, the paper tackles the question of how emotions relate to closely linked processes such as decision-making, distinguishing between parallel architecture models-where emotions and decision-making processes interact but remain distinct-and unified models-where affective states are conceived as integral to goal-oriented processes. Finally, we discuss how our mechanistic proposal can help us address four key questions in animal emotion research: Do animals experience emotions? If so, which animals experience emotions? Which emotions do they experience? And how do these emotions compare to human emotions? The paper concludes by emphasizing the need for further empirical research on the mechanisms of animal emotions and their distinction from other processes.

Late bloomers in play: social isolation and playful skills in an adult bonobo

Social play requires communicative abilities that start developing since the first phases of life. Due to their paedomorphic nature, bonobos (Pan paniscus) tend to maintain a playful attitude also in adulthood. Here, we present the case of an adult bonobo (Congo) that has never had any contact with conspecifics in the first 40 years of life. In 2023, Congo underwent an introduction protocol at the Wilhelma Zoo. Prior to the data collection period, he had spent 8 months within the group. The aim was evaluating Congo's playful social competence and his ability to react in a resilient way to others' stimuli. The play sessions involving Congo and two juveniles (CPSs) were compared with play sessions occurring in other adult-juvenile pairs (OPSs). Compared to OPSs, CPSs were shorter and more punctuated by grooming pauses that were totally absent during OPSs. Despite increased grooming, CPSs had a higher risk of escalation into overt aggression from Congo frequently screaming during the interaction. Unlike other adults, Congo never rapidly replicated the partners' playful facial displays, a phenomenon known as rapid facial mimicry. Despite Congo appearing to struggle to manage social play, he responded to other's invitations, thus indicating a presence of play motivation. Albeit being just a case report, our findings emphasize the importance of adult play as a mechanism for social integration, even in individuals entirely unfamiliar with its nuances. Although animals engage in play early in life, it is never too late to play the game and strengthen social bonds.

Guinea Pig (Cavia porcellus) Welfare: Associations Between Husbandry Practices, Human-Animal Interactions, and Animal Behaviour

Research on the welfare of pet guinea pigs and connections between their behaviour and husbandry practices is scarce. Through an online survey among 1181 German-speaking guinea pig caretakers, we investigated husbandry practices (including social composition, housing type, free roaming, enrichment, and feeding), human-animal interactions, and guinea pig behaviour. Most participating caretakers seemed attentive to their animals' needs and welfare, as shown by the prevalence of self-built enclosures (42.8%) and fenced floor areas (21.1%), with various enrichment and furnishings, and mostly balanced nutrition. Husbandry practices that can negatively impact welfare, such as individual housing and no constant access to hay, were observed for 7.5% and 0.4% of the animals, respectively. Eating and resting next to conspecifics and locomotor play occurred several times per day in 87.6%, 48.1%, and 19.9% of animals, respectively. Biting, running up and down and bar chewing were rare (several times per day in 0.4%, 2.9%, and 0.7% of animals, respectively). We found significant associations of guinea pig behaviour with human-animal interactions and housing conditions. For instance, affiliative behaviour and locomotor play and use of enrichment were more frequently reported in the case of more frequent positive human-animal interactions and food enrichment. Our results provide additional knowledge to support consultations on behaviour and husbandry practices.

Invited review: Social housing of dairy calves-Management factors affecting calf behavior, performance, and health; A systematic review

Given increasing adoption of social housing for preweaning dairy calves, we conducted a systematic review to summarize existing literature describing effects of social housing management factors on behavior, performance, and health of dairy calves. Included articles addressed interventions applied to preweaning, socially housed dairy calves, encompassing age at introduction to social housing, group composition (size, stocking density, within-group age range, stability), and housing environment (space allowance, enrichment provision). Outcome measures addressed behavior, including social behavior, locomotor behavior, feeding behavior, abnormal oral behavior, and behavioral responses during tests; performance, including body measurements and weight gain; and health, including clinical health scores and mortality rate. We conducted searches initially targeting any study where dairy calves were housed socially, using Web of Science and PubMed, and subsequently identified a total of 46 relevant studies. Studies investigating age at introduction to pairs or small social groups of 3 to 7 calves (8 experimental studies) suggested possible behavioral and performance benefits, with no negative effects, of earlier introduction to small groups. Earlier introduction to larger groups (assessed in 6 experimental studies and 4 cross-sectional studies) appeared to increase latency to use an automated milk feeder with short-term negative effects on milk intake, yet no evidence of growth effects and variable health effects. Studies investigating effects of group size (assessed in 8 experimental studies and 6 cross-sectional studies) suggested that small social groups may facilitate increased feeding time, with neutral or positive effects on growth and health. Other aspects of group composition, including within-group age range, group stability, and feeder stocking density, were assessed in few experimental studies (7 total), with some results suggesting behavioral benefits of reducing competition for feed and maintaining stable groups. Experimental and cross-sectional studies yielded conflicting findings with respect to health effects of group composition, but results generally suggested possible health risks associated with larger group sizes and within-group age ranges, management factors consistent with the use of dynamic groups. Increasing space allowance (assessed in 6 experimental studies and 6 cross-sectional studies) increased locomotor activity/play behavior and had neutral or positive health effects. Provision of enrichment items (e.g., brushes, combinations of items for oral manipulation; assessed in 5 studies) was found to reduce cross-sucking. Overall, this review describes varied dairy calf social housing management practices which have implications for behavior, performance, and health. Further work is needed to address gaps in knowledge, including long-term effects and variability at the individual and group level, and to establish the external validity of these findings in commercial settings.

Monkeys increase scratching when encountering unexpected good fortune

Elucidating how ancestral behavioural traits have been repurposed for psychological and social functions is critical to advancing our understanding of human behavioural evolution. Self-scratching, originally a hygienic response and known to exhibit social contagion, serves as a model for this process. Although human scratching behaviour is traditionally linked to negative emotions, evidence from non-human animals has produced inconsistent results, casting doubt on its association with negative emotions. Here, we examined scratching in Japanese macaques (Macaca fuscata) during cognitive tasks. In Experiment 1, we manipulated reward outcomes by introducing rare, unexpected increases ("fortunate" condition) or omissions ("unfortunate" condition) of rewards; scratching increased significantly under the fortunate condition, but not the unfortunate one. In Experiment 2, we presented unexpected visual stimuli without altering reward outcomes and observed increased scratching. Our results challenge the traditional view that scratching is primarily linked to negative emotions. Our findings suggest that scratching, which originally evolved as a response to unexpected skin stimulation, may later have been repurposed as a coping mechanism to manage heightened uncertainty.

The neurobiological basis of emotions and their connection to facial expressions in non-human mammals: insights in nonverbal communication

Recognizing that nonhuman animals are sentient beings has increased interest in studying their emotional state. Similar to humans, research has shown that some nonhuman mammals can modify facial expressions by contraction/relaxation of facial muscles according to their affective state. From a neurophysiological perspective, emotions are processed in several brain structures, mainly from the limbic system, such as the hypothalamus, hypophysis, hippocampus, prefrontal cortex, and amygdala. The converged pathways between the amygdala, the motor cortex, and its projections to the facial nerve control the movement of facial or mimetic muscles. Thus, facial expression is suggested to reflect the internal emotional state and could serve as an essential mode of nonverbal communication in mammals. In humans, the Facial Action Coding System (FACS) is a method that objectively analyzes facial movements using an anatomical base. In veterinary medicine, AnimalFACS is an adaptation of this system to eight animal species, including domestic animals (dogs, cats, and horses) and nonhuman primates (chimpanzees, orangutans, gibbons, macaques, and common marmosets). Considering these coded facial movements, current research aims to associate certain facial expressions with the animals' emotional states and affective contexts. Thus, this review aims to discuss recent findings associated with the neurobiology of emotions and facial expressions in non-human mammals, using AnimalFACS to understand nonverbal communication. Characterizing each facial expression according to different contexts might help identify if the animal is expressing a positive or negative emotional response to the event, which can improve nonverbal human-animal communication.

Effects of Circulation Fans on Broiler Welfare Indicators in Commercial Houses During Cold Seasons

Physical and behavioral characteristics of individual animals can be used as indicators of their welfare status. The objective of this pilot study was to evaluate the effect of circulation fans on indicators of broiler welfare in commercial houses during colder months in the eastern United States. This study was conducted on two flocks of 36,000 straight-run broilers raised in four commercial houses on one farm site, totaling 288,000 birds. Two houses had 16 circulation fans (Fans), and two did not (control, No Fans). At weeks 3 and 6 of age, litter moisture was measured, bird behavior was video recorded, and physical assessments of broiler welfare were conducted. Independent of treatment, mobility and active behaviors decreased as birds aged (p < 0.0001). At week 6, birds in the control houses had a greater prevalence and severity of footpad dermatitis (p = 0.004), hock burn (p = 0.0003), and prevalence of dirty feathers (p < 0.0001). The results of this study indicate that air circulation strategies in commercial houses affect footpad dermatitis, hock burn, and feather cleanliness, providing insight into the impact of circulation fans on indicators of broiler welfare.

A qualitative exploration of owner experiences following dog adoption

The adjustment period - wherein adopted animals transition to their new home - is a critical time for animal welfare and owner satisfaction, yet literature varies in estimates of how long this period lasts in dogs. This study sought to better characterise the adjustment period in relation to owner experience and canine welfare and clarify its duration as perceived by owners. We used a qualitative approach to examine owner perceptions of duration and their experience of the adjustment period. Twenty-seven interviews were conducted and analysed using thematic content analysis. Six themes were described: adjustment period duration; behavioural indicators during adjustment; behaviours indicative of adjustment; factors influencing adjustment; owner change in routine; and adjustment concerns. Over half of participants perceived the adjustment period to last longer than four months. Behaviours used by owners to assess dog adjustment included: moderation of behavioural extremes (e.g. lethargy and restlessness); play; tail wagging; greeting; and learning their routine. Owners reported that prior experiences and medical needs impacted the adjustment duration, that they adjusted aspects of their lifestyle, and raised concerns about being the right fit for their dog. Future research should incorporate a longer time-frame to better understand how and when dogs adjust to a home, and as there is variation in dog behaviour during adjustment, it must also account for individual differences. As we develop a better understanding of how to characterise this period, adopters can be better prepared for the initial months of dog ownership, and interventions can be individualised to improve owner experience and dog welfare.

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.

Levelling up the study of animal gameplay

Play in humans and other animals is widespread and intuitive to recognise. Creative, unstructured play is difficult to quantify, but games direct play towards a specific goal and have defined rules, mechanics and rewards. To date, games have been under-utilised in human and animal behavioural neuroscience. This review evaluates evidence that animals can play human games, including game-theory contests, tangible games, and video games. Animals can be trained to play various human games with cognitive capacities such as role adoption, rule-following and performance monitoring. Animals can make irrational gameplay decisions that jeopardise rewards and have salient emotional responses to winning and losing. Games can advance the field of behavioural neuroscience in several ways. Cognitive tasks can become more engaging and ecologically relevant by adding game elements, known as gamification. Games can be used to induce and measure more naturalistic emotional responses to the process of overcoming (progression/regression) and end state (winning/losing) of cognitive challenges. There is also scope to target specific cognitive skill deficiencies in captive animals using games. However, a recent rapid increase in computerised testing environments raises an important ethical question about the boundary between games and reality for animals.

Exploring the effect of play on heart rate variability as a measure of positive emotional states in pigs

Play behaviour has been suggested to be inherently rewarding for animals, inducing positive emotional states. The psychophysiological effect of emotions can be assessed through heart rate variability (HRV), serving as a proxy measure of sympathovagal balance. This study investigated how the performance of play influences heart rate (HR) and HRV parameters (RMSSD, SDNN) in pigs. It was hypothesized that HRV would increase during and immediately after play due to predominant vagal activation compared to baseline, indicating a positive emotional state. Gilts (n = 32, 18 and 19 weeks of age), housed in standard partly-slatted pens, were selected from two pen-level play treatments: Novelty (NOV) and Play Pen (PLP). Play treatment pigs were reared with intermittent play promotion (3x/week) from 10 weeks of age. For HRV recordings, play was promoted for 15-min in pairs of gilts within treatment, with destructible novel objects given either in the home pen (NOV, 1 m2/pig), or in an enclosed 'playpen' area providing extra space (PLP, 2.9 m2/ pig). HRV was measured during a play session in three consecutive periods: (i) baseline (before play bout, no play occurring), (ii) play bout (play expression), and (iii) after-play (immediately after play bout). Twenty-six gilts played at least once. Play bouts lasted between 10 and 30 s (10 s: n = 60, 20 s: n = 18, 30 s: n = 6). In 10-s bouts, compared to baseline, RMSSD was higher during play (p = 0.027) and after-play (p = 0.015), while SDNN increased during play (p ≤ 0.001) and after-play (p = 0.008) only with ambulation (pig moving forward: walking or running). HR did not differ across periods but was higher at ambulation (p = 0.003). Twenty-sec bouts followed the same relationship with only numerical differences, while HRV in 30-s bouts did not differ. Treatments did not influence HRV. Results suggest that engaging in play increases HRV, with this effect persisting into the period immediately after play. This indicates that play contributes to positive emotional states in pigs. Physical activity involved in play influences HRV. More dynamic and energetic play involving ambulation might be more rewarding for pigs. This study provides evidence for assessing positive emotions in pigs and underscores the importance of incorporating rewarding experiences into conventional farming practices.

Weaning impact: Evaluating growth, behavior, and production performance in Sahiwal cows and their calves

Initial periods of life, beginning before birth and lasting until weaning are characterised by the greatest neural plasticity. Early postnatal stress causes lasting changes in a variety of behaviours as well as stress reactivity. Cow-calf contact for an extended period is believed to improve the social skills of calves and has also been linked to improved productivity of mothers. This research was carried out to investigate the impact of weaning stress on the growth, behaviour and performance of Sahiwal cows and their calves. For this, 32 healthy cows and their calves were selected from the Sahiwal herd of the Livestock Research Centre, ICAR-National Dairy Research Institute. They were grouped equally into two groups of 16 cow-calf pairs, which became the treatment groups (i.e., 'Fenceline' contact and 'Separated' groups). Calves in the fenceline contact group were allowed to suckle during the morning and evening milking and were housed together with fenceline separation. In the separated group, calves were separated from their mothers immediately after birth and fed colostrum and milk with a bottle throughout the experiment. Each calf was monitored for its growth and behavioural responses while cows were monitored for their production performance and behaviour. The results showed that growth and behaviour responses were better for fenceline calves compared to separated calves and also production performance and behaviour of Sahiwal cows provided with fenceline contact were better when compared to separated cows. From this study, it was concluded that fenceline cow-calf contact improved growth, behavioural response of calves; and production performance and behaviour of cows compared to separated cows and calves.

Patterns of object play behaviour and its functional implications in free-flying common ravens

Object play has been proposed to provide individuals with information about their environment, facilitating foraging skills and tool use. In species where object play co-occurs with locomotor or social play, it may have additional functional implications, such as facilitating the evaluation of peers or forming social bonds. For instance, ravens judge others' competitiveness via play caching and engage in social play by exchanging objects. However, most raven studies were conducted on a restricted number of individuals and under controlled captive settings. To validate these findings and to gauge the functional scope of object play under field conditions, we investigated the patterns and characteristics of object play in individually marked free-flying ravens in the Austrian Alps. Using two large data sets, we show a decrease in object play with age and a preference for playing longer with novel objects, supporting findings from captivity. We also find adults occasionally playing with objects and no difference in the duration of social or non-social object play bouts across age classes. Taken together, our findings are in line with the assumption that raven object play likely has more than one function and serves to gain information about the individual's physical and social environment.

Individual variation in activity budgets of a stable population of killer whales in managed care across a year

Activity budget investigations are necessary to understand how individuals within a group manage their daily activities, thus providing insights into the social dynamics of a species. Our objective was to explore and describe the behavioral activities within a group of managed care killer whales. From 261 hours of coded surface video collected from April 2022 to January 2023, we scan-sampled day-time hours to examine eight behavioral categories exhibited by 8-9 killer whales bimonthly. Minimal sex differences were found within each behavioral category across month and hour block. Females exhibited significantly more attention to trainers and rubbing on the environment than males. Individual variability was documented for all behavioral categories. The youngest male showed the most (43 % of scans) proximity and social interactions with conspecifics whereas all adults, both females and males, showed similar levels of social behavior. Three adult females and one adult male spent about a third of all scans observing their trainer(s) as they moved around the habitat. This observational behavior has been described in other delphinids as anticipatory behavior indicating a willingness to participate in future interactions with their trainers whether food rewards were available or not, and has been confirmed to represent a state of positive well-being. All killer whales actively engaged with peers and their environment in about 40 % of the documented scans. These findings are similar in degree to that observed in various other delphinid populations and support the interpretation that this killer whale group is in receive of positive welfare, displaying normal levels of social and individual behaviors for this species. Our results add to the growing body of knowledge about how killer whales manage their actions, both with conspecifics and their environment, across different social settings given their surroundings.

Key Concepts for Enhancing Zoo Animal Welfare: Coping, Comfort, Choice, Control, Challenge, and Compassion

Zoo animal welfare is subject to increasing scrutiny by many audiences. Although zoo husbandry and management techniques have progressed, common welfare issues are still apparent. To encourage further improvements, converting theoretical welfare definition into practical application is key. This paper evaluates a familiar definition to form a baseline for practical welfare assessment that benefits animals and zoo operations. If we consider coping and comfort as measurable indicators, plus choice and control to cement autonomy for the animal, achieving positive welfare is more likely. Providing positive cognitive challenge results in improvements to behavioral diversity. When husbandry is ecologically relevant, this welfare-friendly approach evolves into husbandry-based evidence, further justifying approaches to animal care. The human element of husbandry (e.g., development and training of personnel) impacts on welfare, necessitating a compassionate approach to daily operations. Compassion - for animal and human wellbeing - ultimately embeds welfare as a core zoo goal. The unique environment of the zoo, with its mix of wild species, human workforce and visitors, coupled with the amount we still must learn about species' husbandry needs emphasizes continual development of welfare approaches.

Brush Use in Lot-Fed Cattle Shows Continued Use and Positive Behaviour

Feedlot cattle were assessed for the consistency of enrichment brush use, higher incidence of natural behaviour, and less agonistic or abnormal behaviour compared to cattle without the brush. Cattle were assigned to one of two treatment pens, (1) access to a vertical grooming brush (EB; n = 89) or (2) no access control (CON; n = 80), for a period of 107 days. A Principal Component (PC) analysis was used on pen-side demeanour scores. Statistical analysis on pen-side behaviour and demeanour PCs tested for impact of treatment, day, and time. Frequency of brush use and the duration of each cow-brush interaction did not decrease over the assessment period. Self-grooming and allogrooming did not differ between treatments and were similar in frequency to brush grooming, resulting in total grooming being higher in the EB treatment group (p < 0.05). Cattle in the EB pen were scored as more content (PC 2; p < 0.05) and sociable (PC 3; p < 0.01), while CON cattle were scored as more anxious (PC 3; p < 0.05). Overall, this study suggests that the provision of a brush for enrichment enhanced lot-fed cattle wellbeing and permitted prolonged engagement, making it an effective enrichment device.

Behavioral assessment of well-being in the naïve laboratory ferret (Mustela putorius furo)

Domestic ferrets (Mustela putorius furo) are an emerging model species in biomedical research. While behavioral studies are a critical translational tool for evaluating neurologic function in disease models and toxicology studies, there is a lack of ferret-specific behavioral assays and corresponding data on baseline behavior. Play behavior is a promising target for evaluation of psychological well-being, particularly because ferrets engage in solitary and social play well into adulthood. Therefore, in this study, an ethogram of behaviors associated with play, elevated mood, and environmental interaction was developed and applied in experimentally naïve juvenile and young adult male laboratory ferrets (3 and 6 months of age, respectively). Total play/positive affect behavior was significantly greater in adults relative to juveniles, mostly due to increased dook vocalizations. Juveniles also took significantly longer to first exit into the behavior suite than adults. This may be linked to contextual habituation or a developmentally associated shift in anxiety-like behavior. While the frequency of total environmental interaction did not differ by age, juveniles demonstrated increased exploration of objects whereas young adults engaged in more climbing onto/into objects. Overall, this study provides a simple and efficient method to assess psychological well-being and environmental exploration in both juvenile and young adult laboratory ferrets. Future studies are needed to determine the sensitivity of these measures to neurologic injury or disease.

Husbandry Conditions and Welfare State of Pet Chinchillas (Chinchilla lanigera) and Caretakers' Perceptions of Stress and Emotional Closeness to Their Animals

For pet chinchillas, limited data are available on husbandry and the human-animal relationship despite their impact on health, behavior, and welfare. We conducted an online survey with pet chinchilla caretakers (n = 336), targeting husbandry practices, health, behavioral indicators of welfare, and human-chinchilla relationships. We further investigated associations between caretakers' perceptions of stress in their chinchillas and emotional closeness to their animals. Basic needs such as keeping with conspecifics, constant access to water and hay, or offering dust baths were mostly fulfilled. Potential welfare issues included individual keeping (14.3%), undersized cages/enclosures (reported by 27.6% of the Austrian respondents), and suffering from a disease (14.7%). Behavioral indicators of good welfare, such as playing and cuddling with conspecifics, were observed several times per day by 40.9% and 87.9% of the respondents, respectively. Repetitive and unwanted behaviors were less common (fur biting, for instance, occurred 'never' in 82.9%). Caretakers rated their animals as generally more stressed if the animal was ill and more often showed fearful behavior toward them. Caretakers feeling closer to their animals spent more time engaging with them. Correct identification of this kind of association could be used as guidance for recommendations to improve chinchilla welfare at home and in the veterinary setting.

Friend or foe: effects of social experience and genetic line on responses of young gilts in a social challenge paired interaction test

The increased focus on group housing of sows in commercial pig production emphasises the importance of saving appropriate gilts which later become sows that are well-adapted to group housing systems. This study aimed to assess the short-term effects of social mixing experience and genetic line on social and exploration responses of young gilts in standardised 3-min social challenge paired interaction tests. The study included 96 gilts, from 26 litters, of two different genetic lines (Swedish Yorkshire and Dutch Yorkshire). These lines were chosen because the dam lines have been selected in group-housed and individual stall systems, respectively, a background which was hypothesised to have modified their social behaviour over time. The gilts were subjected to different early (opportunity to co-mingle with piglets in the neighbouring farrowing pen vs. no opportunity to co-mingle) and late (mixed with unfamiliar piglets at weaning vs. kept with familiar littermates after weaning) social mixing treatments, to test whether the enhanced social experience was beneficial in a socially challenging situation. Paired interaction tests were conducted at 5 and 20 weeks of age, and social and exploration behaviour of the gilts was recorded and analysed. The results showed that Swedish Yorkshire gilts explored the pen fittings more than Dutch Yorkshire gilts during the 5-week test, whereas Dutch Yorkshire gilts explored the pen fittings more than Swedish Yorkshire gilts during the 20-week test. No differences in play behaviour were found during the 5-week test, but in the 20-week test, gilts with early social mixing experience in their farrowing pen showed more locomotor play behaviour than gilts without this experience. Overall, these results suggest that genetic line and early social mixing experience can influence the social and exploration behaviours of young gilts in paired interaction tests. There was no support for the hypothesis that genetic selection in different housing systems has altered social behaviour, but it may have affected the level of exploration behaviour. There was little support for our prediction that early social experience has beneficial effects in a socially challenging situation.

Detecting play behaviour in weaned dairy calves using accelerometer data

This research paper describes a validation study evaluating the ability of IceTag accelerometers (Peacock Technology, UK) to detect play behaviour in weaned dairy calves. Play behaviour is commonly observed in young animals and is regarded as an indicator of positive welfare states. Eight Holstein Friesian calves aged three to five months old were monitored using leg-mounted accelerometers for 48 h. Data generated by accelerometers to quantify calf activity included step count, lying times and a proprietary measure of overall activity termed 'motion index' (MI). Calf behaviour was filmed continuously over the same 48-h period using closed circuit television cameras and analysed using one-zero sampling to identify the presence (1) or absence (0) of play within each 15-min time period. A positive correlation between MI and visually recorded play was found. Visual observations were compared with accelerometer-generated data and analysed using 2 × 2 contingency tables and classification and regression tree analysis. A MI value of ≥69 was established as the optimum threshold to detect play behaviour (sensitivity = 94.4%; specificity = 93.6%; balanced accuracy = 94.0%). The results of this study suggest that accelerometer-generated MI data have the potential to detect play behaviour in weaned dairy calves in a more time efficient manner than traditional visual observations.

Pigs in heaven: Enhancing the lives of breeding boars

The recognition of animals as sentient beings has raised societal awareness of the welfare of farmed animals. This has been instrumental in increasing the legislative pressure towards welfare-conscious farming practices and, more lately, greater consumer demand for ethically sourced products. Besides, improved animal welfare is a key driver for enhanced performance, particularly in breeding boars, as welfare conditions strongly influence reproductive outcomes. The stressors associated with confinement impact testicular physiology and semen quality and the efforts to improve the welfare of breeding boars have so far focused on mitigating the negative consequences associated with stressors. The Five Freedoms framework and the European Food Safety Authority (EFSA)'s 'welfare consequences' approach prioritise the alleviation of suffering. In breeding boars, key welfare negative consequences include movement restriction, isolation stress, inability to engage in exploratory behaviours, locomotory disorders, and prolonged hunger. The negative consequences, which can be mitigated by improved housing and management practices, should be tackled in any commitment to improve the welfare of breeding boars. Animal welfare science, however, has recently shifted towards cultivating positive welfare experiences and a life worth living, beyond just alleviating suffering. The Five Domain Model systematically evaluates animal welfare, considering both negative and positive aspects. Encouraging positive welfare states involves facilitating species-specific behaviours, such as exploration and play, and fostering positive human-animal interactions. In breeding boars, strategies promoting positive welfare include providing enriching environments, encouraging exploration, and cultivating positive interactions with caretakers. Thus, for an overall welfare improvement of breeding boars, not only should the absence of suffering be guaranteed, but also the promotion of positive experiences that make their lifes worth living.

Nuancing 'Emotional' Social Play: Does Play Behaviour Always Underlie a Positive Emotional State?

This review focuses on social play, a complex behaviour that is often difficult to categorize. Although play has been typically associated with positive emotional states, a thorough examination of the literature indicates that it may relate to different emotional systems, from attachment to conflict. Play oscillates between competition and cooperation, and includes a spectrum in between; thus, quantitatively identifying and demonstrating the emotional nature of play remains challenging. We considered examples from human and non-human animal studies and explored the emotional and neuro-hormonal systems involved in play. We assessed ethological data possibly indicating the emotional states underlying play, and we focused on the cooperative and competitive elements of play. We investigated the relationship between play and affiliative/aggressive behaviours, the communicative meaning of play signals (especially primate play faces), and the motor and possibly emotional contagion function of rapid motor mimicry during play. From all the literature on play, this review selects and combines studies in an innovative way to present the methods (e.g., play indices and social network analysis), tools (e.g., sequential analysis and facial coding software), and evidence indicative of the emotional states underlying play, which is much more complex than previously thought.

Rearing pigs with play opportunities: the effects on disease resilience in pigs experimentally inoculated with PRRSV

Positive emotions can reduce disease susceptibility during infectious challenges in humans, and emerging evidence suggests similar effects in farm animals. Because play behaviour may support a positive emotional state in pigs, this study investigates whether rearing pigs with regular intermittent play opportunities enhances disease resilience when challenged with porcine reproductive and respiratory syndrome virus (PRRSV). Litters were assigned to either play (PLY; n = 5 L) or control (CON; n = 4 L) treatments at birth. In PLY, play was promoted with extra space and enrichment items for three hours daily from five days of age (doa). At weaning (25 ± 2 doa; mean ± SD), 28 pigs (14/treatment) were selected for a disease challenge, based on weight, sex, and sow. The pigs were transported to a disease containment facility and at 43 ± 2 doa (day 0 post-inoculation, DPI) inoculated with PRRSV. Skin lesions, blood, rectal temperature, clinical signs, body weight, and behaviour were collected pre- and post-inoculation. Play opportunities for PLY continued every other day until euthanasia of all pigs at 65 ± 2 doa (22 DPI). PLY pigs exhibited fewer skin lesions following transport and throughout the infection compared to CON. Although the viral load did not differ between treatments, PLY pigs had a lower probability of experiencing moderate and severe respiratory distress, with a shorter duration. PLY also performed better throughout the infection, showing higher ADG and greater feed efficiency. The immune response differed as well. PLY pigs had fewer monocytes on 8 DPI than CON, with levels returning to baseline by 21 DPI, whereas CON levels exceeded baseline. Regardless of day of infection, lymphocyte counts tended to be lower in PLY than in CON, and white blood cells and neutrophils were also lower, but only in slow-growing pigs. PLY pigs continued to play during the infection, demonstrating less sickness behaviour and emphasizing the rewarding properties of play. Results suggest that PLY pigs were less affected by PRRSV and developed increased resilience to PRRSV compared to CON. This study demonstrates that rearing pigs in an environment supporting positive experiences through provision of play opportunities can enhance resilience against common modern production challenges, underscoring the value of positive welfare in intensive pig farming.

Play contagion in African elephants: The closest, the better

Behavioural contagion is an automatic process through which a behaviour performed by an individual (trigger) is reproduced by an observer (responder) without necessarily replicating the exact motor sequence. It has been linked to inter-individual synchronisation and possibly emotional contagion. Play can convey emotions and enhance social bonding, although its contagiousness is understudied. To verify social play contagion presence and modulating factors, we gathered audio-video data on social play, distance and affiliation on a group of savannah African elephants (15 individuals) at Parque de la Naturaleza de Cabarceno (Cantabria, Spain). Social play was contagious as it was more likely started by uninvolved elephants (within 3-min) in Post-Play Condition (PP) - after that other elephants had started playing - than in Matched-control Condition (MC; no previous play). Social play contagion mostly occurred within 30 m - probably due to elephants' limited visual acuity - and it was highest between individuals that affiliated the most, with the distance-affiliation interaction having no effect. The most prominent individuals in the social play network were also the most influential in the play contagion network (Eigenvector-centrality measure). Play contagion was socially modulated, thus suggesting it may extend from motor replication to the replication of the underlying affective state.

Invited review: The effect of weaning practices on dairy calf performance, behavior, and health-A systematic review

The aim of this systematic review was to summarize the literature assessing the effects of weaning practices on performance, behavior, and health of dairy calves. Only published, peer-reviewed articles written in English and specifically assessing the effects of weaning treatments on dairy calves were eligible for inclusion. Studies had to include 2 or more treatment groups that addressed at least one of 4 interventions: weaning age (i.e., when milk was fully removed), weaning duration (i.e., number of days from start of milk reduction to when milk was fully removed), weaning criteria (e.g., age vs. intake), or alternative weaning methods (e.g., water dilution). Outcome measures could include starter intake, growth (BW or ADG), behaviors (5 specific sucking behaviors; play behavior; lying behavior; vocalizations; unrewarded visits to an automated milk feeder), and health (mortality rate, diarrhea, and respiratory illness). We conducted 3 targeted searches using Web of Science and PubMed. The articles underwent a 2-step screening process, resulting in a final sample of 44 studies. The majority of studies investigated weaning age (n = 22), followed by weaning duration (n = 13), weaning criteria (n = 9), and other weaning methods such as dilution, linear versus step-down milk reduction, or meal-based approaches (n = 6). There was consensus for positive effects (or at least no negative effects) on overall growth of calves weaned at later ages, over longer durations, based on starter intake, or weaned using step-down or meal-based milk removal approaches. This is despite reduced starter intake in calves weaned at later ages; most studies found improved starter intake in calves weaned over longer durations. Weaning based on starter intake had superior growth and feed intakes compared with calves weaned at a fixed earlier age. Few studies assessed interactive effects of weaning method and milk allowance. However, weaning after 8 wk appears to support superior weight gain, provided preweaning milk allowances are adequate (above 6 L/d). Weaning can lead to hunger-related behaviors and reduced welfare, yet only half of the studies assessed the effects of weaning method on calf behavior. Weaning at later ages can reduce signs of hunger (based on unrewarded visits to the milk feeder), but it is unclear if weaning over longer durations or weaning by starter intake reduces or prolongs hunger. There was little consensus among the few studies that measured oral behaviors of calves. Positive welfare indicators, such as play behavior, were rarely measured, yet are crucial to understanding the emotional states of calves during this potentially stressful diet transition. Health was rarely the primary objective of the study, with low sample sizes to conduct statistical comparisons. Overall, there remains significant knowledge gaps in our understanding of how best to wean calves. A successful weaning program must minimize signs of hunger while promoting high growth and feed intakes, so we encourage future work to include behavioral indicators of hunger and positive welfare to evaluate how weaning methods are experienced by the calf.

Can a gradual weaning and separation process reduce weaning distress in dam-reared dairy calves? A comparison with the 2-step method

The weaning and separation phase remains one of the biggest challenges for cow-calf contact systems, but a gradual process that better mimics the naturally occurring reduction in milk intake has not yet been scientifically investigated. Therefore, the aim of our study was to compare behavioral and physiological indicators of distress in 3-mo-old dam-reared dairy calves (with previous full-time cow-calf contact) weaned and separated either via gradual reduction of contact time with the dam (GR; 1 wk of half-day contact, 1 wk of morning contact, and 1 wk of fence-line contact before complete separation, n = 18) or via 2-step weaning using a nose flap (NF, 2 wk of access to the dam with a nose flap, 1 wk of fence-line contact before complete separation, n = 18). Behavior was recorded 1 wk before (or for lying 3 wk before) weaning start and during the 3 wk weaning and separation period with direct observations on 4 d/wk or via accelerometers (locomotor play, lying behavior). Blood and fecal samples were taken twice per week from weaning start until 3 wk after weaning start. Calves were weighed weekly. Statistical analysis was conducted using (generalized) linear mixed models. Over the whole weaning and separation phase, NF calves showed a stronger decrease in the number of lying bouts, amount of locomotor play, and ADG, as well as a higher increase in TMR feeding time compared with GR calves, whereas GR calves vocalized more often and showed more searching behavior than NF calves. Also, the neutrophil:lymphocyte ratio of NF calves was elevated on d 3 after insertion of the nose flaps compared with baseline, but showed no change for GR calves on any sampling day. Overall, results point toward a favorable effect of a gradual weaning strategy on reduction of weaning and separation distress in dam-reared dairy calves, but the method requires further improvement from the protocol used in our study.

Effects of weaning and inactivated Lactobacillus helveticus supplementation on dairy calf behavioral and physiological indicators of affective state

The objectives of this study were to determine if weaning would induce behavioral and physiological indicators of a negative affective state, and if supplementation of inactivated Lactobacillus helveticus (ILH) to dairy calves would reduce those indicators of negative affect during weaning. Male Holstein calves (n = 23) were enrolled in the study on d 1 of life. The calves were housed in individual pens in 1 of 4 rooms for the 42 d study. Calves began a stepdown weaning from 9 L/d of milk replacer (MR), at 150 g of MR powder/L, on d 35 and received 6 L/d on d 35 - 36, 3 L/d on d 37 - 38, and 0.4 L/d on d 39 - 42. The MR was divided between 3 meals/d until the last 0.4 L/d phase which was divided between 2 meals/d. Calves had ad libitum water access throughout the study and calf starter from d 28 onwards. Within room, calves were assigned to 1 of 2 treatments: 1) control (CON; n = 11) and 2) 5 g of ILH/d split over and mixed into the 0800 h and 2000 h milk feedings from d 3-42 (ILH; n = 12). Lying behavior was recorded using HOBO data loggers from d 21-41. On d 33, 37 and 41, infrared eye images were taken to determine maximum eye temperature (MET), saliva samples were collected to determine cortisol concentration, and play assessments were conducted to quantify play behavior. On d 34, 38, and 42, blood samples were collected to determine blood serotonin concentration, whereas on d 38 and 39, calves were tested with a cognitive task. A subset of calves (n = 5/treatment) were euthanized to collect gut and brain tissue samples for serotonin concentration on d 43. Weaning resulted in fewer (d 37-41, tendency: d 36), but longer (d 38-41, tendency: d 37), lying bouts and reduced play (d 41), although no changes in lying time, MET, saliva cortisol, nor blood serotonin were detected with initiation of weaning. Supplementation of ILH was associated with lower lying time throughout the study, and reduced play duration and higher salivary cortisol and MET during weaning. No differences in lying bouts, play count, blood and tissue (colon, ileum, prefrontal cortex and brain stem) serotonin concentration, and time to complete the cognitive task were detected between the treatments. Overall, weaning induced behavioral changes indicative of negative affective state, and some behavioral differences were observed with ILH supplementation both before and during weaning, with some physiological changes observed during weaning.

In praise of folly: flexible goals and human cognition

Humans often pursue idiosyncratic goals that appear remote from functional ends, including information gain. We suggest that this is valuable because goals (even prima facie foolish or unachievable ones) contain structured information that scaffolds thinking and planning. By evaluating hypotheses and plans with respect to their goals, humans can discover new ideas that go beyond prior knowledge and observable evidence. These hypotheses and plans can be transmitted independently of their original motivations, adapted across generations, and serve as an engine of cultural evolution. Here, we review recent empirical and computational research underlying goal generation and planning and discuss the ways that the flexibility of our motivational system supports cognitive gains for both individuals and societies.

Music and Emotions in Non-Human Animals from Biological and Comparative Perspectives

The effects of sound stimulation as a sensorial environmental enrichment for captive animals have been studied. When appropriately implemented for farm animals, it can improve welfare, health, and productivity. Furthermore, there are indications that music can induce positive emotions in non-human animals, similar to humans. Emotion is a functional state of the organism involving both physiological processes, mediated by neuroendocrine regulation, and changes in behavior, affecting various aspects, including contextual perception and welfare. As there is very limited information on non-human animals, the objective of this review is to highlight what is known about these processes from human biological and comparative perspectives and stimulate future research on using music to improve animal welfare.

Quantification of play behaviour in calves using automated ultra-wideband location data and its association with age, weaning and health status

Play behaviour can act as an indicator of positive animal welfare. Previous attempts to predict play behaviour in farmed calves are limited because of the classification methods used, which lead to overestimation, and the short time periods that calves are observed. The study aimed to automatically classify and quantify play behaviour in farmed calves using location data from ultra-wide band sensors and to investigate factors associated with play behaviour. Location data were collected from 46 calves in three cohorts for a period of 18 weeks. Behavioural observations from video footage were merged with location data to obtain a total of 101.36 h of labelled data. An AdaBoost ensemble learning algorithm was implemented to classify play behaviour. To account for overestimation, generally seen in low-prevalence behaviours, an adjusted count technique was applied to the outputs of the classifier. Two generalized linear mixed models were fitted to investigate factors (e.g. age, health) associated with duration of play and number of play instances per day. Our algorithm identified play behaviour with > 94% accuracy when evaluated on the test set with no animals used for training, and 16% overestimation, which was computed based on the predicted number of samples of play versus the number of samples labelled as play on the test set. The instances and duration of play behaviour per day significantly decreased with age and sickness, whilst play behaviour significantly increased during and after weaning. The instances of play also significantly decreased as mean temperature increased. We suggest that the quantification method that we used could be used to detect and monitor other low prevalence behaviours (e.g. social grooming) from location data, including indicators of positive welfare.

Benefit of Cognitive Environmental Enrichments on Social Tolerance and Play Behavior in Bottlenose Dolphins (Tursiops Truncatus)

Social tolerance is an essential feature of social life that can determine the good functioning of a group of animals. Play behaviors, like social play and playing with objects, are frequently associated with positive emotional and welfare states. As a result, zoos use various strategies to promote both social tolerance and play with objects. Providing animals with cognitive environmental enrichment can be an effective tool to achieve these goals. Here we tested whether cognitive environmental enrichment can promote social tolerance and play with objects in bottlenose dolphins (Tursiops truncatus). To this end, we provided a group of five dolphins with two types of cognitive enrichment: one for individual use and one for cooperative use, both based on the rope-pulling task paradigm. Then we evaluated whether social tolerance and play with objects had increased after we provided dolphins with the two enrichments. Our results go in this direction, showing that after we provided dolphins with the enrichments, their intolerance behaviors decreased, both during feeding sessions and play sessions, while their play with objects increased. As a result, the two enrichments we used could be useful for improving dolphins' housing conditions.

Finding biomarkers of experience in animals

At a time when there is a growing public interest in animal welfare, it is critical to have objective means to assess the way that an animal experiences a situation. Objectivity is critical to ensure appropriate animal welfare outcomes. Existing behavioural, physiological, and neurobiological indicators that are used to assess animal welfare can verify the absence of extremely negative outcomes. But welfare is more than an absence of negative outcomes and an appropriate indicator should reflect the full spectrum of experience of an animal, from negative to positive. In this review, we draw from the knowledge of human biomedical science to propose a list of candidate biological markers (biomarkers) that should reflect the experiential state of non-human animals. The proposed biomarkers can be classified on their main function as endocrine, oxidative stress, non-coding molecular, and thermobiological markers. We also discuss practical challenges that must be addressed before any of these biomarkers can become useful to assess the experience of an animal in real-life.

Resource choice during ontogeny enhances both the short- and longer-term welfare of laying hen pullets

We hypothesised that resource choice during early life contributes to both current and longer-term beneficial effects on animal welfare. We investigated this hypothesis in a longitudinal cross-over experiment with laying hen pullets (Gallus gallus domesticus) reared in pens with one or four litter and perch types, respectively (n = 8 pens/treatment, all providing ample and identical litter and perch space). After 4 weeks (chick period), half the pens were modified to provide the opposite treatment (juvenile period). After 11 more weeks, all groups were moved to novel, identical laying pens (adult period; Week 16-27). In support of our hypothesis, the opportunity to choose between multiple litter and perch variants was associated with higher levels of positively-valenced behaviours, including play as chicks and dustbathing as juveniles and adults, and lower levels of negatively-valenced behaviours, including feather pecking as chicks and juveniles and aggressive pecking as adults. Resource choice in the juvenile period also led to better juvenile and adult plumage condition, and greater growth as adults. We conclude that the opportunity to choose among different litter and perch types, instead of having only one type of each, had both short- and longer-term positive effects on the birds' affective states and physical condition.

Play Behavior Varies with Age, Sex, and Socioecological Context in Wild, Immature Orangutans (Pongo spp.)

Play is thought to serve different purposes at different times during ontogeny. The nature and frequency of play are expected to change accordingly over the developmental trajectory and with socio-ecological context. Orangutans offer the opportunity to disentangle the ontogenetic trajectories of solitary and social play with their extended immature phase, and socio-ecological variation among populations and species. We evaluated the frequency of play in 39 immature individuals across two populations (Pongo pygmaeus wurmbii, at Tuanan, Borneo, and P. abelii at Suaq, Sumatra), age (0-11 years), sex, and social context, using more than 11 500 h of full-day focal observation data. We found independent age trajectories of different play types, with solitary object and solitary locomotor peaking before social play. Social play partners changed during ontogeny, and male immatures were more likely to engage in non-mother social play than females. Overall, social play was more frequent at Suaq than Tuanan, linked to the more frequent availability of partners. Furthermore, per time in association with conspecifics, Tuanan immatures were as likely to engage in social play as their peers at Suaq, suggesting similar intrinsic motivation. Increasing fruit availability correlated with both longer associations and increased social play frequency in the less sociable population of Tuanan, but not at Suaq. Our findings on orangutans support evidence from other species that different play types follow different developmental trajectories, vary with sex, social opportunities, and ecological context. Although drawing functional inferences is challenging, the distinct developmental trajectories reflecting adult sociability and behavioral repertoires may indicate that play serves several, non-mutually exclusive functions during ontogeny.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10764-023-00414-2.

Cognitive Group Testing Promotes Affiliative Behaviors in Dolphins

Ex-situ research in aquariums and zoological settings not only support scientific advancement, they also provide opportunities for education, facilitating both mental and physical stimulation, consequently improving welfare. This study aimed to investigate the impact of cognitive testing on the well-being of a group of male Indo-Pacific bottlenose dolphins. The occurrence of affiliative, aggressive and potentially stereotypical behaviors was assessed based on seven monitored behavior types and compared between "Session days" and "Non-session days." The consistency of the impact was assessed over a three-year period. The analyses revealed that "Play with enrichment," "Affiliative tactile," "Social play" and "Synchronous swim" were significantly higher, while "Aggression" was significantly lower on Session days than on Non-session days. Individual analysis showed significant increase in the positive welfare indicators in all dolphins during Session days. The social network analysis of aggressive interactions between group members also supported an overall decrease of aggression during Session days. These results indicate that dolphin groups that voluntarily participate in cognitive tests under human care benefit from the testing and show an improvement in animal welfare while contributing to scientific advancement.

Effects of free farrowing system on the productive performance and welfare of sows and piglets

Regardless of international animal welfare regulations, most sows in production currently spend most of their lives and the peripartum period in caged housing systems. Although this type of management is intended to reduce neonatal mortality in piglets, several studies consider that there has been no significant reduction in its incidence over the last 30 years. On the contrary, cage housing has promoted the appearance of alterations during the farrowing process such as dystocia, as well as in maternal behavior and health, promoting stereotypes, skin lesions and other alterations, which not only impact the sows but also their progeny during the lactational period. Therefore, the aim of the present review is to compare the productive performance and welfare of sows and their piglets within the farrowing, lactation, and post-weaning period in both traditional and free-farrowing systems, highlighting the differences in these indicators in each of them.

Object Play as a Positive Emotional State Indicator for Farmed Spotted Paca (Cuniculus paca)

We aimed to assess whether object play can be used as a positive emotional state indicator for farmed spotted pacas (Cuniculus paca) by examining its association with other positive welfare markers including affiliative behavior and low-amplitude vocalizations. We submitted six groups of spotted pacas (one male/two females per group) (N = 18) to an ABA experimental design (A1/A2: without ball; B: with three boomer balls). Object play behavior occurred only during phase B (mean = 35.5 s, SE = 6.4). The spotted pacas spent more time in affiliative and exploratory behaviors and less time engaging in agonistic interactions during phase B than in both control phases (A1 and A2) (p < 0.05). Moreover, the spotted pacas emitted more low-amplitude bark vocalizations during phase B than during either control phase (p < 0.05), and such vocalizations have previously been shown to indicate a positive affective state and low arousal level. Because the expression of object play was associated with a decrease in aggression, an increase in affiliative behavior, and an increase in low-amplitude barking, we suggest that object play can be used as a non-invasive indicator of positive emotional state in this species.

The agency domain and behavioral interactions: assessing positive animal welfare using the Five Domains Model

Animal welfare denotes how an animal experiences their life. It represents the overall mental experiences of an animal and is a subjective concept that cannot be directly measured. Instead, welfare indicators are used to cautiously infer mental experiences from resource provisions, management factors, and animal-based measures. The Five Domains Model is a holistic and structured framework for collating these indicators and assessing animal welfare. Contemporary approaches to animal welfare management consider how animals can be given opportunities to have positive experiences. However, the uncertainty surrounding positive mental experiences that can be inferred has resulted in risk-averse animal welfare scientists returning to the relative safety of positivism. This has meant that aspects of positive welfare are often referred to as animal 'wants'. Agency is a concept that straddles the positivist-affective divide and represents a way forward for discussions about positive welfare. Agency is the capacity of individual animals to engage in voluntary, self-generated, and goal-directed behavior that they are motivated to perform. Discrete positive emotions are cautiously inferred from these agentic experiences based on available knowledge about the animal's motivation for engaging in the behavior. Competence-building agency can be used to evaluate the potential for positive welfare and is represented by the Behavioral Interactions domain of the Five Domains Model. In 2020, The Model was updated to, amongst other things, include consideration of human-animal interactions. The most important aspect of this update was the renaming of Domain 4 from "Behavior" to "Behavioral Interactions" and the additional detail added to allow this domain's purpose to be clearly understood to represent an animal's opportunities to exercise agency. We illustrate how the Behavioral Interactions domain of The Model can be used to assess animals' competence-building agency and positive welfare. In this article, we use the examples of sugar gliders housed in captivity and greyhounds that race to illustrate how the agentic qualities of choice, control, and challenge can be used to assess opportunities for animals to exercise agency and experience positive affective engagement.

Manatees in Zoological Parks throughout the World: History, State, and Welfare

The order Sirenia comprises several species of manatees and one species of dugong. These popular marine mammals are relatively recent acquisitions to zoological parks throughout the world. As far as we know, there are less than 200 manatees, mostly American, a few African, and ever less Amazonian, currently in zoological parks. American manatees are predominantly found in zoos in Europe, North America, and in some Asian countries, while African ones are present exclusively in Asian zoos. The living conditions of captive manatees differ considerably from zoo to zoo (i.e., numbers, sex ratio, outdoor vs. indoor habitats, complex vs. simple habitats). Most research on manatee behaviour has been relatively recent, and studies on cognition, sociality, and ecology have a significant impact on our perception of manatee needs and management, with wider implications for their welfare. In the wild, manatees demonstrated various cognitive capacities; spatial memory and learning abilities play an important role in their daily life in a complex and dynamic environment. Furthermore, there is evidence that these mammals are more social animals than expected. Individuals show various personality traits on the boldness-shyness continuum and their sociality varies. All those parameters are important in terms of animal welfare. Several behavioural studies showed that standardized enrichment programs benefit and ensure the welfare of captive zoo animals. However, obtaining accurate information on the presence of manatees in zoos, living conditions, management, and consequently welfare remains challenging. This study examines the current knowledge on manatee behaviour and cognition and then discusses different approaches to improving the welfare of this charismatic marine mammal in zoological parks.

Joyful by nature: approaches to investigate the evolution and function of joy in non-human animals

The nature and evolution of positive emotion is a major question remaining unanswered in science and philosophy. The study of feelings and emotions in humans and animals is dominated by discussion of affective states that have negative valence. Given the clinical and social significance of negative affect, such as depression, it is unsurprising that these emotions have received more attention from scientists. Compared to negative emotions, such as fear that leads to fleeing or avoidance, positive emotions are less likely to result in specific, identifiable, behaviours being expressed by an animal. This makes it particularly challenging to quantify and study positive affect. However, bursts of intense positive emotion (joy) are more likely to be accompanied by externally visible markers, like vocalisations or movement patterns, which make it more amenable to scientific study and more resilient to concerns about anthropomorphism. We define joy as intense, brief, and event-driven (i.e. a response to something), which permits investigation into how animals react to a variety of situations that would provoke joy in humans. This means that behavioural correlates of joy are measurable, either through newly discovered 'laughter' vocalisations, increases in play behaviour, or reactions to cognitive bias tests that can be used across species. There are a range of potential situations that cause joy in humans that have not been studied in other animals, such as whether animals feel joy on sunny days, when they accomplish a difficult feat, or when they are reunited with a familiar companion after a prolonged absence. Observations of species-specific calls and play behaviour can be combined with biometric markers and reactions to ambiguous stimuli in order to enable comparisons of affect between phylogenetically distant taxonomic groups. Identifying positive affect is also important for animal welfare because knowledge of positive emotional states would allow us to monitor animal well-being better. Additionally, measuring if phylogenetically and ecologically distant animals play more, laugh more, or act more optimistically after certain kinds of experiences will also provide insight into the mechanisms underlying the evolution of joy and other positive emotions, and potentially even into the evolution of consciousness.

Non-invasive assessment of positive affective state using infra-red thermography in rats

With recent increased focus on positive welfare in animal welfare science, there is demand for objective positive welfare indicators. It is unclear whether changes in body surface temperature can be used to non-invasively identify and quantify positive states in mammals. We recorded continuous measurements of tail surface temperature using infra-red thermography (IRT) and concurrent behavioural observations in male and female Wistar rats (Rattus norvegicus). If tail surface temperature can differentiate between positive and negative experiences, we expect a qualitatively different response compared to negative experiences. Three groups of rats were presented with increasing magnitudes of food rewards (neutral/none, one and three rewards). The rats were placed in an arena to which they were habituated and filmed for 30 s before and 30 min after exposure to different rewards. Tail temperature initially decreased from the pre-reward baseline and subsequently returned towards baseline temperature. The overall pattern of the change was the same as for rats subjected to negative stimuli in previous studies. Nevertheless, dynamic changes in tail temperature, specifically the rate of recovery and the behavioural response (exploration), differed between neutral and rewarded rats but failed to distinguish reward magnitude. Sex differences were found in both thermal and behavioural responses, unrelated to reward magnitudes. Female rats exhibited a greater initial response with a slower recovery than male rats, emphasising the value of using of both sexes in animal welfare research. This study improves our understanding of the effects of positive emotions induced by food reward on peripheral body temperature and behaviour.

Is it for real? Structural differences between play and real fighting in adult chimpanzees (Pan troglodytes)

In primates, as well as in other mammals, play fighting (PF) is a complex form of playful activity that is structurally similar to real fighting (RF) and may also be used in a competitive way. Here, we verify the structural key differences that can distinguish PF from RF in adult chimpanzees (Pan troglodytes). We collected 962 h of video recording on 30 adult individuals belonging to four chimpanzee groups (Mona Chimpanzee Sanctuary, Spain; La Vallée des Singes and ZooParc de Beauval, France). We applied different indices-two of which were borrowed from the ecological measures of biodiversity-to test for structural differences between PF (345 sessions) and RF (461 sessions) in the levels of behavior repetition (Repeatability of Same Behavior Index, RSBI), distribution uniformity (Pielou Index, J), variability (Shannon Index, H') and, symmetry (i.e., reciprocal exchange of offensive/defensive behaviors; Asymmetry Index, AI). Moreover, we compared the session duration between PF and RF. We found that duration and RSBI were higher in PF than RF while AI was higher in RF than PF. No difference was found between J and H'. Interestingly, both females and males maintained similar ranking positions (determined via Normalized David's scores) in RF and PF. Our study indicates that session duration, behavior repetition, and symmetry can be distinctive structural key features of PF whereas dominance role-reversal, behavior variability, and distribution uniformity were not. PF in adult chimpanzees may have elements of serious contexts (e.g., absence of role-reversal as in RF) which is in line with the view that play is a blended, multifunctional behavior deriving from the re-combination of different behavioral systems. Our findings highlight the need to investigate play structure and manifestation in a nuanced way to better understand the actual motivation that underlies what appears to be play.

Invited review: The effect of milk feeding practices on dairy calf behavior, health, and performance-A systematic review

The aim of this systematic review was to summarize the literature assessing the effects of milk feeding practices on behavior, health, and performance on dairy calves. Peer-reviewed, published articles, written in English, directly comparing the effects of milk allowance, milk feeding methods, or milk feeding frequency on dairy calves were eligible for inclusion. Outcome measures could include sucking behavior, sucking on a teat (nutritive sucking, non-nutritive sucking on a teat), abnormal sucking behavior (non-nutritive sucking on pen fixtures, other oral behaviors, or cross-sucking), signs of hunger (vocalizations or unrewarded visits at the milk feeder), activity (lying time or locomotor play), feeding behavior (milk intake, starter intake, milk meal duration, or starter meal duration), growth (body weight or average daily gain), and health (occurrence of diarrhea, respiratory disease, or mortality). We conducted 2 targeted searches using Web of Science and PubMed to identify key literature. The resulting articles underwent a 2-step screening process. This process resulted in a final sample of 94 studies. The majority of studies investigated milk allowance (n = 69). Feeding higher milk allowances had a positive or desirable effect on growth, reduced signs of hunger, and increased locomotor play behavior during the preweaning period, whereas starter intake was reduced. Studies addressing health pointed to no effect of milk allowance, with no consistent evidence indicating that higher milk allowances result in diarrhea. Studies addressing milk feeding methods (n = 14) found that feeding milk by teat reduced cross-sucking and other abnormal oral behaviors. However, results on the effect of access to a dry teat were few and mixed. Milk feeding frequency (n = 14 studies) appeared to have little effect on feed intakes and growth; however, there is some evidence that calves with lower feeding frequency experience hunger. Overall, findings strongly suggest feeding higher volumes of milk using a teat; however, further work is needed to determine the optimal feeding frequency for dairy calves.

The neurobiology of social play behaviour: Past, present and future

Social play behaviour is a highly energetic and rewarding activity that is of great importance for the development of brain and behaviour. Social play is abundant during the juvenile and early adolescent phases of life, and it occurs in most mammalian species, as well as in certain birds and reptiles. To date, the majority of research into the neural mechanisms of social play behaviour has been performed in male rats. In the present review we summarize studies on the neurobiology of social play behaviour in rats, including work on pharmacological and genetic models for autism spectrum disorders, early life manipulations and environmental factors that influence play in rats. We describe several recent developments that expand the field, and highlight outstanding questions that may guide future studies.

The practicality of practice: A model of the function of play behaviour

The function of play has been a long-debated topic in animal behaviour. One popular class of accounts is that play offers practice for serious adult behaviour, but little has been done to model the circumstances where this could be true. In this paper, we model an individual who, over the juvenile and subadult ontogenetic periods, has a choice between three behaviours: foraging, playing and rest, where playing improves an individual's ability in some component of a serious adult behaviour. Using stochastic dynamic programming, we show that even when play is more energetically costly and an inferior form of practice than foraging itself, it still may be optimal to play under a variety of circumstances. We offer several instantiations of the play as practice concept to show the possibility of play improving a variety of different adult abilities: antipredatory, foraging and reproductive behaviour. These models show the environmental conditions where play might be expected, as well as the predicted occurrences of play throughout ontogeny. This is a first step in showing the ecological feasibility of the practice hypothesis of play and raises further questions about why playful activity is more beneficial than more deliberate directed practice.

Ear health and quality of life in pet rabbits of differing ear conformations: A UK survey of owner-reported signalment risk factors and effects on rabbit welfare and behaviour

The impacts of ear disease on animal welfare and behaviour are little documented. Ear disease may be common in rabbits, but difficult to recognise, and lop-ears have previously been indicated as a risk factor for ear disease. We aimed to better understand the range of ear conditions in pet rabbits, signalment risk factors, and impacts on welfare and behaviour. Through an online questionnaire, we investigated owner-reported signalment, veterinary diagnosis of ear conditions, impaired hearing, and ear pain for UK pet rabbits. Relationships between ear condition measures and ear conformation, quality of life, and behaviour were analysed using logistic regression. Of 551 valid responses, 28.5% of rabbits reportedly had experienced ear conditions; 21.2% diagnosed or mentioned by vets, with otitis and excess cerumen most common. Approximately 25% of lop-eared rabbits had ear conditions indicated by a vet versus 10% of erect-eared rabbits. Lop-eared, half-lop, and older rabbits were most at risk (P<0.050). Rabbits reported as showing ear pain responses had reduced owner-reported quality of life compared with other rabbits (P<0.050). Rabbits with ear problems were less likely to be responsive to relevant sounds, and performed binky behaviour (joy jumps) less frequently, than rabbits without such issues. Understanding prevalence and risk factors for ear conditions is critical to improving welfare standards across this widely owned pet species. The findings suggest that improved recognition and treatment of ear conditions, and avoiding breeding from rabbits with early signs, or a family history, of ear disease are necessary to help combat this animal welfare issue.

Handling and Training of Wild Animals: Evidence and Ethics-Based Approaches and Best Practices in the Modern Zoo

There is an ethical responsibility to provide all animals living in human care with optimal and positive well-being. As animals living in zoos and aquariums frequently interact with their human caregivers as part of their daily care routines, it is both relevant and essential to consider the impact of these interactions on animal well-being. Allowing animals to have choice and control in multiple areas of their lives, such as by providing opportunities for them to voluntarily participate in their own care through, for example, positive reinforcement training, is an essential component of good animal well-being programs. This review aims to describe evidence-based approaches, ethics, and best practices in the handling and training of the many taxa held in zoos and aquariums worldwide, drawing from work in related animal care fields such as laboratories, farms, rescue, and sanctuaries. The importance of ongoing animal well-being assessments is discussed, with a particular focus on the need for continued review and refinement of processes and procedures pertaining to animal training and handling specifically. Review, enquiry, assessment, evaluation, and refinement will aim to dynamically support positive well-being for all animals.

Social and locomotor play behavior of dairy calves kept with the dam either full time or half time in straw-bedded pens

This study investigated play behavior of dairy calves kept with the cow either full time or half time in groups of 4 dam-calf pairs in 68-m² straw-bedded pens. Twenty-four of 48 calves entering the experiment (2 calves in each of 12 pens) were observed during 24 h at 3 and 7 wk of age. The total duration of locomotor play did not differ between the 2 treatments, but full-time calves performed less frontal pushing (social play). Irrespective of treatment, calves performed less parallel locomotor play and more frontal pushing at 7 wk than 3 wk of age. Analyzing the intensity of play behavior during milking times (morning and afternoon, respectively), during the night and between morning and afternoon milking, showed that calves performed locomotor play more intensively after the cows had left the pen for milking than during other periods. The results illustrate the importance of space and external stimulation for the performance of play behavior.