Unpredictable movement as an anti-predator strategy.

Prey animals have evolved a wide variety of behaviours to combat the threat of predation, and these have been generally well studied. However, one of the most common and taxonomically widespread antipredator behaviours of all has, remarkably, received almost no experimental attention: so-called 'protean' behaviour. This is behaviour that is sufficiently unpredictable to prevent a predator anticipating in detail the future position or actions of its prey. In this study, we used human 'predators' participating in 3D virtual reality simulations to test how protean (i.e. unpredictable) variation in prey movement affects participants' ability to visually target them as they move (a key determinant of successful predation). We found that targeting accuracy was significantly predicted by prey movement path complexity, although, surprisingly, there was little evidence that high levels of unpredictability in the underlying movement rules equated directly to decreased predator performance. Instead, the specific movement rules differed in how they impacted on targeting accuracy, with the efficacy of protean variation in one element depending on the values of the remaining elements. These findings provide important insights into the understudied phenomenon of protean antipredator behaviour, which are directly applicable to predator-prey dynamics within a broad range of taxa.

The impact of egg incubation temperature on the personality of oviparous reptiles.

Personality traits, defined as differences in the behavior of individual animals of the same species that are consistent over time and context, such as 'boldness,' have been shown to be both heritable and be influenced by external factors, such as predation pressure. Currently, we know very little about the role that early environmental factors have upon personality. Thus, we investigated the impact of incubation temperature upon the boldness on an oviparous reptile, the bearded dragon (Pogona vitticeps). Eggs, from one clutch, were incubated at two different average temperatures within the normal range. After hatching the lizards were raised under the same environmental conditions. Novel object and novel environment tests were used to assess personality. Each test was repeated in both the short term and the long term. The results revealed that incubation temperature did impact upon 'boldness' but only in the short term and suggests that, rather than influencing personality, incubation temperature may have an effect on the development of behavioral of oviparous reptiles at different stages across ontogeny.

Long-term memory of relative reward values.

Long-term memory can be adaptive as it allows animals to retain information that is crucial for survival, such as the appearance and location of key resources. This is generally examined by comparing choices of stimuli that have value to the animal with those that do not; however, in nature choices are rarely so clear cut. Animals are able to assess the relative value of a resource via direct comparison, but it remains unclear whether they are able to retain this information for a biologically meaningful amount of time. To test this, captive red-footed tortoises (Chelonoidis carbonaria) were first trained to associate visual cues with specific qualities and quantities of food, and their preferences for the different reward values determined. They were then retested after an interval of 18 months. We found that the tortoises were able to retain the information they had learned about the cues as indicators of relative reward values over this interval, demonstrating a memory for the relative quantity and quality of food over an extended period of time. This is likely to impact directly on an animal's foraging decisions, such as the exploitation of seasonally varying resources, with obvious fitness implications for the individual; however, the implications may also extend to the ecological interactions in which the animal is involved, affecting processes such as herbivory and seed dispersal.

A reappraisal of successive negative contrast in two populations of domestic dogs.

When an anticipated food reward is unexpectedly reduced in quality or quantity, many mammals show a successive negative contrast (SNC) effect, i.e. a reduction in instrumental or consummatory responses below the level shown by control animals that have only ever received the lower-value reward. SNC effects are believed to reflect an aversive emotional state, caused by the discrepancy between the expected and the actual reward. Furthermore, how animals respond to such discrepancy has been suggested to be a sign of animals' background mood state. However, the occurrence and interpretation of SNC effects are not unequivocal, and there is a relative lack of studies conducted outside of laboratory conditions. Here, we tested two populations of domestic dogs (24 owned pet dogs and 21 dogs from rescue kennels) in a SNC paradigm following the methodology by Bentosela et al. (J Comp Psychol 123:125-130, 2009), using a design that allowed a within-, as well as a between-, subjects analysis. We found no evidence of a SNC effect in either population using a within- or between-subjects design. Indeed, the within-subjects analysis revealed a reverse SNC effect, with subjects in the shifted condition showing a significantly higher level of response, even after they received an unexpected reduction in reward quality. Using a within-, rather than a between-, subjects design may be beneficial in studies of SNC due to higher sensitivity and statistical power; however, order effects on subject performance need to be considered. These results suggest that this particular SNC paradigm may not be sufficiently robust to replicate easily in a range of environmental contexts and populations.

Animal welfare: a social networks perspective.

Social network theory provides a useful tool to study complex social relationships in animals. The possibility to look beyond dyadic interactions by considering whole networks of social relationships allows researchers the opportunity to study social groups in more natural ways. As such, network-based analyses provide an informative way to investigate the factors influencing the social environment of group-living animals, and so has direct application to animal welfare. For example, animal groups in captivity are frequently disrupted by separations, reintroductions and/or mixing with unfamiliar individuals and this can lead to social stress and associated aggression. Social network analysis ofanimal groups can help identify the underlying causes of these socially-derived animal welfare concerns. In this review we discuss how this approach can be applied, and how it could be used to identify potential interventions and solutions in the area of animal welfare.

Humans can identify reward-related call types of chickens.

Humans can decode emotional information from vocalizations of animals. However, little is known if these interpretations relate to the ability of humans to identify if calls were made in a rewarded or non-rewarded context. We tested whether humans could identify calls made by chickens (Gallus gallus) in these contexts, and whether demographic factors or experience with chickens affected their correct identification context and the ratings of perceived positive and negative emotions (valence) and excitement (arousal) of chickens. Participants (n = 194) listened to eight calls when chickens were anticipating a reward, and eight calls in non-rewarded contexts, and indicated whether the vocalizing chicken was experiencing pleasure/displeasure, and high/low excitement, using visual analogue scales. Sixty-nine per cent of participants correctly assigned reward and non-reward calls to their respective categories. Participants performed better at categorizing reward-related calls, with 71% of reward calls classified correctly, compared with 67% of non-reward calls. Older people were less accurate in context identification. Older people's ratings of the excitement or arousal levels of reward-related calls were higher than younger people's ratings, while older people rated non-reward calls as representing higher positive emotions or pleasure (higher valence) compared to ratings made by younger people. Our study strengthens evidence that humans perceive emotions across different taxa, and that specific acoustic cues may embody a homologous signalling system among vertebrates. Importantly, humans could identify reward-related calls, and this ability could enhance the management of farmed chickens to improve their welfare.

Simulating individual movement in fish.

Accurately quantifying an animal's movement is crucial for developing a greater empirical and theoretical understanding of its behaviour, and for simulating biologically plausible movement patterns. However, we have a relatively poor understanding of how animals move at fine temporal scales and in three-dimensional environments. Here, we collected high temporal resolution data on the three-dimensional spatial positions of individual three-spined sticklebacks (Gasterosteus aculeatus), allowing us to derive statistics describing key geometric characteristics of their movement and to quantify the extent to which this varies between individuals. We then used these statistics to develop a simple model of fish movement and evaluated the biological plausibility of simulated movement paths using a Turing-type test, which quantified the association preferences of live fish towards animated conspecifics following either 'real' (i.e., based on empirical measurements) or simulated movements. Live fish showed no difference in their response to 'real' movement compared to movement simulated by the model, although significantly preferred modelled movement over putatively unnatural movement patterns. The model therefore has the potential to facilitate a greater understanding of the causes and consequences of individual variation in movement, as well as enabling the construction of agent-based models or real-time computer animations in which individual fish move in biologically feasible ways.

Model aversiveness and the evolution of imperfect Batesian mimics.

There are numerous examples of Batesian mimics that only imperfectly resemble their models. Given that inaccurate mimics are known to be predated more frequently than accurate ones, imperfect mimicry therefore poses something of a conundrum. One putative explanation, the relaxed selection hypothesis, predicts that when the cost of attacking a model is high relative to the benefit of consuming a mimic, selection against imperfect mimics will be relaxed, allowing mimics to be more imperfect for a given level of fitness. However, empirical support for this hypothesis is equivocal. Here, we report an experimental test of the relaxed selection hypothesis, in which human participants were tasked with discriminating between artificial stimuli representing models and mimics. In response to "attacking" a model (i.e., misclassifying it as palatable, or non-aversive) they received either a mild electric shock (high cost) or vibratory feedback (low cost). Consistent with the predictions of this hypothesis, we found that when the cost of attacking a model was high, mimetic phenotype could deviate more from the model (i.e., be more imperfect) for a given level of fitness than when the cost of attacking a model was low. Moreover, when the cost of attacking a model was high, participants showed an increased latency to attack. This finding shows that given sufficient costs, the relaxed selection hypothesis is a plausible explanation for the evolution of imperfect mimicry.

Changes in group behaviour in response to a preferred environment reflect positive affect.

When observed in their preferred environments, animals display behavioural changes, such as an increase in resting or a reduction in agonism, suggestive of positive affect and improved welfare. However, most studies focus on the behaviour of individuals or, at most, pairs of animals; even though in group-living animals beneficial environmental changes may impact on how the group behaves as a whole. In this study, we investigated whether experiencing a preferred visual environment affected the shoaling behaviour of zebrafish (Danio rerio) groups. We first confirmed a group preference for an image of gravel placed underneath the base of a tank compared to a plain white image. Second, we observed replicated groups either with or without the preferred (gravel) image present to determine if a visually enriched and preferred environment could elicit changes in shoaling behaviour. We found a significant interaction between the observation time and test condition, with differences in shoaling behaviour reflective of increased relaxation emerging gradually over time in the gravel condition. The findings of this study reveal that experiencing a preferred environment can alter group behaviour, making such holistic changes valuable as potential indicators of positive welfare.

An integrative and functional framework for the study of animal emotion and mood.

A better understanding of animal emotion is an important goal in disciplines ranging from neuroscience to animal welfare science. The conscious experience of emotion cannot be assessed directly, but neural, behavioural and physiological indicators of emotion can be measured. Researchers have used these measures to characterize how animals respond to situations assumed to induce discrete emotional states (e.g. fear). While advancing our understanding of specific emotions, this discrete emotion approach lacks an overarching framework that can incorporate and integrate the wide range of possible emotional states. Dimensional approaches that conceptualize emotions in terms of universal core affective characteristics (e.g. valence (positivity versus negativity) and arousal) can provide such a framework. Here, we bring together discrete and dimensional approaches to: (i) offer a structure for integrating different discrete emotions that provides a functional perspective on the adaptive value of emotional states, (ii) suggest how long-term mood states arise from short-term discrete emotions, how they also influence these discrete emotions through a bi-directional relationship and how they may function to guide decision-making, and (iii) generate novel hypothesis-driven measures of animal emotion and mood.

How to Handle Your Dragon: Does Handling Duration Affect the Behaviour of Bearded Dragons (Pogona Vitticeps)?

Reptiles are popular as pets and it is, therefore, important to understand how different aspects of housing and husbandry impact on their behaviour and welfare. One potential cause of stress in captive reptiles is interaction with humans; in particular, the effect of handling. However, little research on handling has been carried out with reptiles, particularly relating to the type of gentle handling likely to be experienced by pet animals. The aim of this study was therefore to determine whether the amount of time that bearded dragons (Pogona vitticeps), a commonly kept pet species, experienced gentle handling induced no or differing levels of anxiety, as reflected in their subsequent behavioural response to novelty. We found that there appeared to be a mildly aversive effect of handling time on subsequent behavioural response to novelty. Longer durations of handling (5 min or 15 min) appeared to increase anxiety-related behaviour, with handled animals showing more frequent tongue flicking behaviour when they experienced a novel environment and reduced time spent in close proximity to a novel object. These results suggest that handling bearded dragons, even in a gentle way, may increase their anxiety. However, it is not yet known whether animals may habituate to handling for longer periods if provided with additional experience.

Assessing the External Validity of Successive Negative Contrast - Implications for Animal Welfare.

When unexpectedly switched from a preferred to a less-preferred food reward, non-human animals may decrease consumption below that when only receiving the less-preferred reward - a successive negative contrast (SNC) effect. SNC has been proposed as an animal welfare indicator, however, to be effective it should show external validity; being demonstrable outside of highly standardized laboratory settings. We therefore investigated whether the SNC effect typically shown in laboratory rats was observed in owned (pet) rats from heterogeneous non-laboratory environments. Subjects (N = 14) were tested in a consummatory SNC paradigm with solid food rewards. "Shifted" rats received a high-value reward for 10 days (pre-shift), a low-value reward for six days (post-shift), then one additional day of high-value reward (re-shift). "Unshifted" rats always received the same low-value reward. "Shifted" rats consumed more food during pre-shift and re-shift trials, but ate less of the low-value food than "unshifted" animals in the post-shift trials - a SNC effect. This confirms the external validity of the SNC paradigm, extending reproducibility to outside the laboratory, indicating translatability across contexts, thus enhancing its potential use as a welfare indicator.

Stress-induced changes in group behaviour.

Testing animals in groups can provide valuable data for investigating behavioural stress responses. However, conventional measures typically focus on the behaviour of individual animals or on dyadic interactions. Here, we aimed to determine metrics describing the behaviour of grouping animals that can reveal differences in stress responses. Using zebrafish (Danio rerio) as a model, we observed replicated shoals both immediately and 24 hours after exposure to a novel environment, as an assessment of temporal change in response to an acute stressor. We quantified various standard behavioural measures in combination with metrics describing group structure, including different proximity, social, and spatial metrics. Firstly, we showed a high collinearity between most of the analysed metrics, suggesting that they describe similar aspects of the group dynamics. After metric selection, we found that under acute stress shoals had significantly higher shoal densities, a lower variation in nearest neighbour distances and were in closer proximity to the walls compared to the same groups tested 24 hours later, indicating a reduction in acute stress over time. Thus, the use of group metrics could allow for the refinement of behavioural protocols carried out in a range of research areas, by providing sensitive and rich data in a more relevant social context.

Developing Diagnostic Frameworks in Veterinary Behavioral Medicine: Disambiguating Separation Related Problems in Dogs.

Diagnoses are widely used in both human and veterinary medicine to describe the nature of a condition; by contrast, syndromes are collections of signs that consistently occur together to form a characteristic presentation. Treatment of syndromes, due to either their lack of a clear biological cause or multiple causes, necessarily remains non-specific. However, the discovery of interventions may help refine the definition of a syndrome into a diagnosis. Within the field of veterinary behavioral medicine, separation related problems (SRPs) provide a good example of a syndrome. We describe here a comprehensive process to develop a diagnostic framework (including quality control assessments), for disambiguating the signs of SRPs as an example of a heterogeneous behavioral syndrome in non-human animals requiring greater diagnostic and treatment precision. To do this we developed an online questionnaire (243 items) that covered the full spectrum of theoretical bases to the syndrome and undertook a large-scale survey of the presenting signs of dogs with one or more of the signs of SRPs (n = 2,757). Principal components analysis (n1 = 345), replicated in a second sample (n2 = 417; total n = 762), was used to define the structure of variation in behavioral presentation, while hierarchical agglomerative cluster analysis cross checked with the partitioned around medoids method was used to determine sub-populations. A total of 54 signs were of value in defining a latent structure consisting of seven principal components (termed "exit frustration," "social panic," "elimination," "redirected frustration," "reactive communication," "immediate frustration," "noise sensitivity"), which divided the population in four clusters (termed "exit frustration," "redirected reactive," "reactive inhibited" and "boredom" related SRPs) with 11 sub-clusters (3, 3, 3, and 2, respectively). We used a bottom-up data-driven approach with numerous quality checks for the definition of robust clusters to provide a robust methodology for nosological studies in veterinary behavioral medicine, that can extend our understanding of the nature of problems beyond SRPs. This provides a solid foundation for future work examining aetiological, and differential treatment outcomes, that will allow both more effective treatment and prevention programmes, based on a fully appreciation of the nature of the problem of concern.

A novel task to assess mood congruent memory bias in non-human animals.

BACKGROUND: Assessing the affective state of animals is important for a range of research areas, including neuroscience. The use of cognitive judgement and attention biases to determine affective state has been demonstrated in animals, but approaches to assess mood-congruent biases in memory have yet to become established. NEW METHOD: We describe a novel methodology to investigate memory bias in animals, presenting initial data using the influence of social status to manipulate affective state. The method required laboratory rats to achieve criterion at a working-memory task in an eight-arm radial maze before probing their memory of putative negative, positive or neutral events that occurred in specific arms of the maze. They were tested 2 h and 24 h after experiencing each event to determine how the affective valence of the event influenced task performance. RESULTS: Regardless of social status, rats avoided arms where they had experienced negative events and preferred arms where they had experienced positive events. However, subordinate rats made errors sooner than dominant rats in tests following exposure to the negative event. Furthermore, whilst subordinate individuals made errors earlier in tests following the negative event relative to the neutral or positive event, dominant rats made errors earlier in tests that followed the positive event. COMPARISON WITH EXISTING METHOD(S): Changes in performance thus appeared to reflect social status and associated affective state, confirming a new method for assessing animal affect. CONCLUSIONS: This new memory bias task could potentially be used to determine affective state in a range of non-human animal species.

Behavioural responses to unexpected changes in reward quality.

Successive negative contrast (SNC) effects are changes in anticipatory or consummatory behaviour when animals unexpectedly receive a lower value reward than they have received previously. SNC effects are often assumed to reflect frustration and appear to be influenced by background affective state. However, alternative explanations of SNC, such as the functional-search hypothesis, do not necessarily imply an aversive affective state. We tested 18 dogs in a SNC paradigm using a patch foraging task. Dogs were tested in two conditions, once with the low value reward in all of five trials (unshifted) and once when reward value was altered between high and low (shifted). Following a reward downshift, subjects showed a SNC effect by switching significantly more often between patches compared to the unshifted condition. However, approach latency, foraging time and quantity consumed did not differ between conditions, suggesting non-affective functional search behaviour rather than frustration. There was no relationship between strength of SNC and anxiety-related behaviours as measured in a novel object test and a personality questionnaire (C-BARQ). However, associations with the C-BARQ scores for Trainability and Stranger directed aggression suggest a possible link with behavioural flexibility and coping style. While reward quality clearly affects incentive motivation, the relationship between SNC, frustration and background affective state requires further exploration.

Can Sleep and Resting Behaviours Be Used as Indicators of Welfare in Shelter Dogs (Canis lupus familiaris)?

Previous research on humans and animals suggests that the analysis of sleep patterns may reliably inform us about welfare status, but little research of this kind has been carried out for non-human animals in an applied context. This study explored the use of sleep and resting behaviour as indicators of welfare by describing the activity patterns of dogs (Canis lupus familiaris) housed in rescue shelters, and comparing their sleep patterns to other behavioural and cognitive measures of welfare. Sleep and activity patterns were observed over five non-consecutive days in a population of 15 dogs. Subsequently, the characteristics of sleep and resting behaviour were described and the impact of activity on patterns of sleep and resting behaviour analysed. Shelter dogs slept for 2.8% of the day, 14.3% less than previously reported and experienced less sleep fragmentation at night (32 sleep bouts). There were no statistically significant relationships between behaviours exhibited during the day and sleep behaviour. A higher proportion of daytime resting behaviour was significantly associated with a positive judgement bias, less repetitive behaviour and increased time spent coded as 'relaxed' across days by shelter staff. These results suggest that, in the context of a busy shelter environment, the ability to rest more during the day could be a sign of improved welfare. Considering the non-linear relationship between sleep and welfare in humans, the relationship between sleep and behavioural indicators of welfare, including judgement bias, in shelter dogs may be more complex than this study could detect.

The influence of preexperimental experience on social discrimination in rats (Rattus norvegicus).

The authors used laboratory rats (Rattus norvegicus) of known relatedness and contrasting familiarity to assess the potential effect of preexperimental social experience on subsequent social recognition. The authors used the habituation-discrimination technique, which assumes that multiple exposures to a social stimulus (e.g., soiled bedding) ensure a subject discriminates between the habituation stimulus and a novel stimulus when both are introduced simultaneously. The authors observed a strong discrimination if the subjects had different amounts of preexperimental experience with the donors of the 2 stimuli but a weak discrimination if the subjects had either equal amounts of preexperimental experience or no experience with the stimuli. Preexperimental social experience does, therefore, appear to influence decision making in subsequent social discriminations. Implications for recognition and memory research are discussed.

Recognition of conspecific odors by laboratory rats (Rattus norvegicus) does not show context specificity.

This experiment investigated how contextual cues affect recognition of conspecific odors in laboratory rats (Rattus norvegicus). Rats received 5 encounters with the same odor in the same context. For the 6th test encounter, all rats received a simultaneous presentation of the original odor and a novel odor. The authors tested 1 group of rats (context same) in the same context as before. For the remaining 2 groups, the test encounter was in a different context that 1 group (context different) had experienced but that 1 group (context novel) had not. A significant preference to investigate the novel odor by context-same and context-different rats, but not by context-novel rats, suggests that odor recognition can occur following transfer to a different, but familiar, test context, indicating a lack of context specificity.

Housing conditions affect rat responses to two types of ambiguity in a reward-reward discrimination cognitive bias task.

Decision-making under ambiguity in cognitive bias tasks is a promising new indicator of affective valence in animals. Rat studies support the hypothesis that animals in a negative affective state evaluate ambiguous cues negatively. Prior automated operant go/go judgement bias tasks have involved training rats that an auditory cue of one frequency predicts a Reward and a cue of a different frequency predicts a Punisher (RP task), and then measuring whether ambiguous cues of intermediate frequency are judged as predicting reward ('optimism') or punishment ('pessimism'). We investigated whether an automated Reward-Reward (RR) task yielded similar results to, and was faster to train than, RP tasks. We also introduced a new ambiguity test (simultaneous presentation of the two training cues) alongside the standard single ambiguous cue test. Half of the rats experienced an unpredictable housing treatment (UHT) designed to induce a negative state. Control rats were relatively 'pessimistic', whilst UHT rats were quicker, but no less accurate, in their responses in the RR test, and showed less anxiety-like behaviour in independent tests. A possible reason for these findings is that rats adapted to and were stimulated by UHT, whilst control rats in a predictable environment were more sensitive to novelty and change. Responses in the new ambiguity test correlated positively with those in single ambiguous cue tests, and may provide a measure of attention bias. The RR task was quicker to train than previous automated RP tasks. Together, they could be used to disentangle how reward and punishment processes underpin affect-induced cognitive biases.