Exploring the similarities between risk factors triggering depression in humans and elevated in-cage "inactive but awake" behavior in laboratory mice.

Introduction: Depression is a human mental disorder that can also be inferred in non-human animals. This study explored whether time spent inactive but awake ("IBA") in the home-cage in mice was further triggered by risk factors similar to those increasing vulnerability to depression in humans (early life stress, genetic predispositions, adulthood stress). Methods: Eighteen DBA/2 J and 18 C57BL/6 J females were tested, of which half underwent as pups a daily maternal separation on post-natal days 2-14 (early-life stress "ELS") (other half left undisturbed). To assess the effect of the procedure, the time the dams from which the 18 subjects were born spent active in the nest (proxy for maternal behavior) was recorded on post-natal days 2, 6, 10 and 14 for 1 h before separation and following reunion (matched times for controls), using live instantaneous scan sampling (total: 96 scans/dam). For each ELS condition, about half of the pups were housed post-weaning (i.e., from 27 days old on average) in either barren (triggering IBA and depression-like symptoms) or larger, highly enriched cages (n = 4-5 per group). Time mice spent IBA post-weaning was observed blind to ELS treatment using live instantaneous scan sampling in two daily 90-min blocks, two days/week, for 6 weeks (total: 192 scans/mouse). Data were analyzed in R using generalized linear mixed models. Results: The dams were significantly more active in the nest over time (p = 0.016), however with no significant difference between strains (p = 0.18), ELS conditions (p = 0.20) and before/after separation (p = 0.83). As predicted, post-weaning barren cages triggered significantly more time spent IBA in mice than enriched cages (p < 0.0001). However, neither ELS (p = 0.4) nor strain (p = 0.84) significantly influenced time mice spent IBA, with no significant interaction with environmental condition (ELS × environment: p = 0.2861; strain × environment: p = 0.5713). Discussion: Our results therefore only partly support the hypothesis that greater time spent IBA in mice is triggered by risk factors for human depression. We discuss possible explanations for this and further research directions.

Spatial working memory in a disappearing object task is impaired in female but not male dogs with chronic osteoarthritis.

Chronic pain in humans is associated with impaired working memory but it is not known whether this is the case in long-lived companion animals, such as dogs, who are especially vulnerable to developing age-related chronic pain conditions. Pain-related impairment of cognitive function could have detrimental effects on an animal's ability to engage with its owners and environment or to respond to training or novel situations, which may in turn affect its quality of life. This study compared the performance of 20 dogs with chronic pain from osteoarthritis and 21 healthy control dogs in a disappearing object task of spatial working memory. Female neutered osteoarthritic dogs, but not male neutered osteoarthritic dogs, were found to have lower predicted probabilities of successfully performing the task compared to control dogs of the same sex. In addition, as memory retention interval in the task increased, osteoarthritic dogs showed a steeper decline in working memory performance than control dogs. This suggests that the effects of osteoarthritis, and potentially other pain-related conditions, on cognitive function are more clearly revealed in tasks that present a greater cognitive load. Our finding that chronic pain from osteoarthritis may be associated with impaired working memory in dogs parallels results from studies of human chronic pain disorders. That female dogs may be particularly prone to these effects warrants further investigation.

A primer on the use of computational modelling to investigate affective states, affective disorders and animal welfare in non-human animals.

Objective measures of animal emotion-like and mood-like states are essential for preclinical studies of affective disorders and for assessing the welfare of laboratory and other animals. However, the development and validation of measures of these affective states poses a challenge partly because the relationships between affect and its behavioural, physiological and cognitive signatures are complex. Here, we suggest that the crisp characterisations offered by computational modelling of the underlying, but unobservable, processes that mediate these signatures should provide better insights. Although this computational psychiatry approach has been widely used in human research in both health and disease, translational computational psychiatry studies remain few and far between. We explain how building computational models with data from animal studies could play a pivotal role in furthering our understanding of the aetiology of affective disorders, associated affective states and the likely underlying cognitive processes involved. We end by outlining the basic steps involved in a simple computational analysis.

Do you see what I see? Testing horses' ability to recognise real-life objects from 2D computer projections.

The use of 2-dimensional representations (e.g. photographs or digital images) of real-life physical objects has been an important tool in studies of animal cognition. Horses are reported to recognise objects and individuals (conspecifics and humans) from printed photographs, but it is unclear whether image recognition is also true for digital images, e.g. computer projections. We expected that horses trained to discriminate between two real-life objects would show the same learnt response to digital images of these objects indicating that the images were perceived as objects, or representations of such. Riding-school horses (N = 27) learnt to touch one of two objects (target object counterbalanced between horses) to instantly receive a food reward. After discrimination learning (three consecutive sessions of 8/10 correct trials), horses were immediately tested with on-screen images of the objects over 10 image trials interspersed with five real object trials. At first image presentation, all but two horses spontaneously responded to the images with the learnt behaviour by contacting one of the two images, but the number of horses touching the correct image was not different from chance (14/27 horses, p > 0.05). Only one horse touched the correct image above chance level across 10 image trials (9/10 correct responses, p = 0.021). Our findings thus question whether horses recognise real-life objects from digital images. We discuss how methodological factors and individual differences (i.e. age, welfare state) might have influenced animals' response to the images, and the importance of validating the suitability of stimuli of this kind for cognitive studies in horses.

A mapping review of refinements to laboratory rat housing and husbandry.

Refining the housing and husbandry of laboratory rats is an important goal, both for ethical reasons and to allow better quality research. We conducted a mapping review of 1,017 studies investigating potential refinements of housing and husbandry of the laboratory rat to assess what refinements have, and have not, been studied, and to briefly assess whether there is evidence to support any impact on rat welfare. Among the many refinements studied, the majority involve changes to the cage, but some also involve alterations to the wider environment. The effects of these refinements were assessed using a range of readouts, many of which are difficult to interpret from a welfare perspective. Preference studies, which are easier to interpret, provide evidence that rats prefer complex environments, including shelters and multiple objects, which offer different areas/resources allowing the rat to engage in diverse behaviors. The reporting of methodology in papers was often poor, indicating that studies were potentially subject to biases. Given that many refinements co-occurred, it was often difficult to tease apart which ones were most beneficial for rat welfare. Effects of refinements were also moderated by a number of factors including age, sex, strain and photoperiod. Altogether our findings show that a one-size-fits-all approach to refinements is not appropriate, because different refinements will impact different rats in different ways. Our review has also produced a database of >1,000 articles that can be used for further and more detailed analyses. Our findings have also highlighted areas where future research is likely to be valuable, including refinements to rat transport, handling and the use of training.

Developing guidelines for pet rat housing through expert consultation.

BACKGROUND: Pet care guidelines play an important role in ensuring that owners are well informed about good husbandry practices, allowing them to provide the best care for their animals. However, the development of such guidelines is difficult when there is little appropriate empirical evidence on which to base guidelines, as in the case of pet rats. The consultation of multiple experts can help to surmount this challenge. METHODS: We developed a set of guidelines for pet rat housing by consulting with a group of experts, including veterinarians, veterinary nurses, animal welfare scientists and experienced pet rat owners. The consultation involved two rounds of online surveys (n = 13) and one online discussion (n = 8). RESULTS: The resulting guidelines cover a broad range of features within pet rat housing, including injury prevention, details of suitable refuges and substrates, and suitable cage sizing. The guidelines may evolve as more information about pet rats comes to light but may nonetheless provide a useful starting point for any future guidelines. CONCLUSIONS: At present, these guidelines may not only be useful for pet rat owners and those advising pet rat owners, such as veterinarians, but may also be useful in the design of housing, including for laboratory rodents.

Responses to environmental enrichment are associated with personality characteristics in chestnut-bellied seed finches (Sporophila angolensis).

Environmental enrichment (EE) is used to promote natural behaviours in captive animals and may hold promise as a form of pre-release training, a strategy for improving coping skills of translocated birds. We investigated the use of EE to enhance foraging and vigilance behaviours of captive Sporophila angolensis, which may be related to post-release survival. We also evaluated whether consistent individual behavioural differences affected birds' responses to EE. We submitted 19 captive seed-finches to three short-term challenges: tonic immobility (TI), new environment (NE) and new object (NO) tests. TI behaviour is related to fear/escape response to potential predators and novelty tests (NE and NO) assess neophobia, which are ecologically relevant personality traits influencing the shyness-boldness continuum. We noted a pronounced variability among the individuals' personality traits, both in their fear and escape-related responses in the TI test and along shy/bold z-scores in NE and NO tests. During a period of enrichment, birds spent more time foraging and less time in vigilance states compared with both control phases. Personality traits of the birds affected their responses to enrichment with bolder birds spending more time foraging. The EE-related decrease in vigilance was independent of the birds' personality traits. Our findings highlight interactions between personality and rearing environment that may impact post-release outcomes for translocated animals.

Validation of complementary non-invasive tools for stress assessment in spotted paca (Cuniculus paca).

Monitoring the concentration of glucocorticoid metabolites (GCMs) in faecal samples is a non-invasive tool for physiological stress evaluation, particularly useful when studying wild species. However, both negative and positive stimuli (distress and eustress, respectively) can lead to a rise in glucocorticoids. Thus, besides validating whether GCM concentration in faeces reflects endogenous adrenal activity, we also need to identify behavioural indicators of distress to avoid misinterpretation. Therefore, we submitted four adult male spotted pacas (Cuniculus paca) to an exogenous adrenocorticotropic hormone (ACTH) challenge-test in a Latin square design (4 × 4) to monitor changes in the GCM concentration in faeces. We also aimed to describe behaviours potentially indicative of distress. We collected excreted faeces and video-recorded the animals' behaviours for five consecutive days, one day before and four days after application of the following four treatments: 1st control (no-handling); 2nd control (intra-muscular [IM] injection of saline solution); low-dose ACTH (IM injection of 0.18 ml ACTH); and high-dose ACTH (IM injection of 0.37 ml ACTH). There was a peak in the concentration of GCM in faeces collected 24 h after the injection of the high-dose ACTH treatment. Additionally, independent of the treatments, spotted pacas spent less time on exploration and feeding states, while spending more time in the inactive but awake (IBA) state following the treatment application (challenge day). The use of GCM concentration in faecal samples together with the behavioural changes (less exploration and feeding, and more IBA) showed to be efficient as a non-invasive tool for welfare assessment of farmed spotted paca.

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.

Bridging the Gap: Human Emotions and Animal Emotions.

Our experiences of the conscious mental states that we call emotions drive our interest in whether such states also exist in other animals. Because linguistic report can be used as a gold standard (albeit indirect) indicator of subjective emotional feelings in humans but not other species, how can we investigate animal emotions and what exactly do we mean when we use this term? Linguistic reports of human emotion give rise to emotion concepts (discrete emotions; dimensional models), associated objectively measurable behavioral and bodily emotion indicators, and understanding of the emotion contexts that generate specific states. We argue that many animal studies implicitly translate human emotion concepts, indicators and contexts, but that explicit consideration of the underlying pathways of inference, their theoretical basis, assumptions, and pitfalls, and how they relate to conscious emotional feelings, is needed to provide greater clarity and less confusion in the conceptualization and scientific study of animal emotion.

Haematology, physiological parameters, morphometry and parasitological status of rescued bearded capuchin monkeys (Sapajus libidinosus).

BACKGROUND: There are few studies on the physiology and haematology of rescued bearded capuchin monkeys. These are necessary to better understand the health and welfare status of the animals, including when performing reintroductions, and to avoid zoonoses. METHODS: We aimed to obtain physiological and haematological values, morphometry and parasitological status of 26 bearded capuchins in two rescue centres in Northeast Brazil. RESULTS: We found sex- and age-related differences in respiratory rate, body weight and body mass index, but not haematology. The haematological values obtained were significantly different from published data but within the reference intervals for the species. Animals infected with Ancylostoma spp. had significantly lower values in the parameters: haemoglobin concentration, mean corpuscular volume and mean corpuscular haemoglobin concentration than non-infected individuals. CONCLUSION: Physiological and haematological values of rescued capuchins were similar to those found in previous studies. Ancylostomiasis appears to cause alterations to haematological values of this species.

Stage 1 Registered Report: Refinement of tickling protocols to improve positive animal welfare in laboratory rats.

Rat tickling is a heterospecific interaction for experimenters to mimic the interactions of rat play, where they produce 50 kHz ultrasonic vocalisations (USV), symptoms of positive affect; tickling can improve laboratory rat welfare. The standard rat tickling protocol involves gently pinning the rat in a supine position. However, individual response to this protocol varies. This suggests there is a risk that some rats may perceive tickling as only a neutral experience, while others as a positive one, depending on how tickling is performed. Based on our research experiences of the standard tickling protocol we have developed a playful handling (PH) protocol, with reduced emphasis on pinning, intended to mimic more closely the dynamic nature of play. We will test whether our PH protocol gives rise to more uniform increases in positive affect across individuals relative to protocols involving pinning. We will compare the response of juvenile male and female Wistar rats as: Control (hand remains still against the side of the test arena), P0 (PH with no pinning), P1 (PH with one pin), P4 (PH with four pins). P1 and P4 consist of a background of PH, with treatments involving administration of an increasing dosage of pinning per PH session. We hypothesise that rats exposed to handling protocols that maximise playful interactions (where pinning number per session decreases) will show an overall increase in total 50 kHz USV as an indicator of positive affect, with less variability. We will explore whether behavioural and physiological changes associated with alterations in PH experience are less variable. We propose that maximising the numbers of rats experiencing tickling as a positive experience will reduce the variation in response variables affected by tickling and increase the repeatability of research where tickling is applied either as a social enrichment or as a treatment.

Do greater levels of in-cage waking inactivity in laboratory mice reflect a spontaneous depression-like symptom? A pharmacological investigation.

We previously identified in laboratory mice an inactive state [being awake with eyes open motionless within the home cage; inactive but awake, 'IBA'] sharing etiological factors and symptoms with human clinical depression. We further test the hypothesis that greater time spent displaying IBA indicates a depression-like state in mice by investigating whether the antidepressant Venlafaxine, environmental enrichment, and their combination, alleviate IBA. Seventy-two C57BL/6J and 72 DBA/2J female mice were pseudo-randomly housed post-weaning in mixed strain-pairs in non-enriched (NE; 48 pairs) or in environmentally enriched (EE; 24 pairs) cages. After 34 days, half of the mice housed in NE cages were either relocated to EE cages or left in NE cages. For each of these conditions, half of the mice drank either a placebo or the antidepressant Venlafaxine (10 mg/kg). The 48 mice housed in EE cages were all relocated to NE cages and allocated to either the placebo (n = 24) or Venlafaxine (n = 24). IBA data were collected prior to and after environmental adjustment by trained observers blind to the pharmacological and environmental adjustment treatments. Data were analyzed using GLM models. NE cages triggered more IBA than EE cages (Likelihood-Ratio-Test Chi23 = 53.501, p < 0.0001). Venlafaxine and environmental enrichment appeared equally effective at reducing IBA (LRT Chi23 = 18.262, p < 0.001), and combining these approaches did not magnify their effects. Enrichment removal triggered IBA increase (LRT Chi21 = 23.050, p < 0.001), but Venlafaxine did not overcome the increase in IBA resulting from enrichment loss (LTR Chi21 = 0.081, p = 0.775). Theoretical implications for putative depression-like states in mice, and further research directions, are discussed.

A Systematic Review of the Use of Technology to Monitor Welfare in Zoo Animals: Is There Space for Improvement?

A top priority of modern zoos is to ensure good animal welfare (AW), thus, efforts towards improving AW monitoring are increasing. Welfare assessments are performed through more traditional approaches by employing direct observations and time-consuming data collection that require trained specialists. These limitations may be overcome through automated monitoring using wearable or remotely placed sensors. However, in this fast-developing field, the level of automated AW monitoring used in zoos is unclear. Hence, the aim of this systematic literature review was to investigate research conducted on the use of technology for AW assessment in zoos with a focus on real-time automated monitoring systems. The search led to 19 publications with 18 of them published in the last six years. Studies focused on mammals (89.5%) with elephant as the most studied species followed by primates. The most used technologies were camera (52.6%) and wearable sensors (31.6%) mainly used to measure behaviour, while the use of algorithms was reported in two publications only. This research area is still young in zoos and mainly focused on large mammals. Despite an increase in publications employing automated AW monitoring in the last years, the potential for this to become an extra useful tool needs further research.

Nature calls: intelligence and natural foraging style predict poor welfare in captive parrots.

Understanding why some species thrive in captivity, while others struggle to adjust, can suggest new ways to improve animal care. Approximately half of all Psittaciformes, a highly threatened order, live in zoos, breeding centres and private homes. Here, some species are prone to behavioural and reproductive problems that raise conservation and ethical concerns. To identify risk factors, we analysed data on hatching rates in breeding centres (115 species, 10 255 pairs) and stereotypic behaviour (SB) in private homes (50 species, 1378 individuals), using phylogenetic comparative methods (PCMs). Small captive population sizes predicted low hatch rates, potentially due to genetic bottlenecks, inbreeding and low availability of compatible mates. Species naturally reliant on diets requiring substantial handling were most prone to feather-damaging behaviours (e.g. self-plucking), indicating inadequacies in the composition or presentation of feed (often highly processed). Parrot species with relatively large brains were most prone to oral and whole-body SB: the first empirical evidence that intelligence can confer poor captive welfare. Together, results suggest that more naturalistic diets would improve welfare, and that intelligent psittacines need increased cognitive stimulation. These findings should help improve captive parrot care and inspire further PCM research to understand species differences in responses to captivity.

Third-party conflict interventions are kin biased in captive white-lipped peccaries (Mammalia, Tayassuidae).

Third-party interventions may regulate conflicts to reduce aggression and promote cohesion amongst group members, but are rarely documented in ungulates. The white-lipped peccary (Tayassu pecari) lives in mixed-sex herds of hundreds of individuals in Neotropical forests, which are likely to benefit from mechanisms that sustain social cohesiveness. We examined third-party conflict interventions between individuals in captive groups of white-lipped peccaries. During a period of 60 days, we recorded agonistic interactions and occurrences of third-party conflict interventions, and estimated the genetic relatedness between the individuals involved using multilocus microsatellite genotypes. Most third-party conflict interventions were by the dominant male of each group, resulting in conflict termination 100% of the time. Our results also revealed that white-lipped peccaries favour their closest relatives and that individuals showed lower levels of aggression towards kin than to non-kin, and interventions on behalf of kin were more frequent than on behalf of non-kin. Our findings support the idea that genetic relatedness is fundamental in both social structure and third-party conflict interventions in this species, allowing us to suggest that kin selection could have a key role in the evolution of social behaviour of white-lipped peccaries.

Using Primary Reinforcement to Enhance Translatability of a Human Affect and Decision-Making Judgment Bias Task.

Good translatability of behavioral measures of affect (emotion) between human and nonhuman animals is core to comparative studies. The judgment bias (JB) task, which measures "optimistic" and "pessimistic" decision-making under ambiguity as indicators of positive and negative affective valence, has been used in both human and nonhuman animals. However, one key disparity between human and nonhuman studies is that the former typically use secondary reinforcers (e.g., money) whereas the latter typically use primary reinforcers (e.g., food). To address this deficiency and shed further light on JB as a measure of affect, we developed a novel version of a JB task for humans using primary reinforcers. Data on decision-making and reported affective state during the JB task were analyzed using computational modeling. Overall, participants grasped the task well, and as anticipated, their reported affective valence correlated with trial-by-trial variation in offered volume of juice. In addition, previous findings from monetary versions of the task were replicated: More positive prediction errors were associated with more positive affective valence, a higher lapse rate was associated with lower affective arousal, and affective arousal decreased as a function of number of trials completed. There was no evidence that more positive valence was associated with greater "optimism," but instead, there was evidence that affective valence influenced the participants' decision stochasticity, whereas affective arousal tended to influence their propensity for errors. This novel version of the JB task provides a useful tool for investigation of the links between primary reward and punisher experience, affect, and decision-making, especially from a comparative perspective.

Dogs are more pessimistic if their owners use two or more aversive training methods.

Domestic dogs are trained using a range of different methods, broadly categorised as reward based (positive reinforcement/negative punishment) and aversive based (positive punishment/negative reinforcement). Previous research has suggested associations between use of positive punishment-based techniques and undesired behaviours, but there is little research investigating the relative welfare consequences of these different approaches. This study used a judgement bias task to compare the underlying mood state of dogs whose owners reported using two or more positive punishment/negative reinforcement based techniques, with those trained using only positive reinforcement/negative punishment in a matched pair study design. Dogs were trained to discriminate between rewarded and unrewarded locations equidistant from a start box, and mean latencies recorded. Their subsequent latency to intermediate 'ambiguous' locations was recorded as an indication of whether these were perceived as likely to contain food or not. Dogs trained using aversive methods were slower to all ambiguous locations. This difference was significant for latency to the middle (Wilcoxon Z = - 2.380, P = 0.017), and near positive (Wilcoxon Z = - 2.447, P = 0.014) locations, suggesting that dogs trained using coercive methods may have a more negative mood state, and hence that there are welfare implications of training dogs using such methods.