Neophobia in 10 ungulate species-a comparative approach

A Metric-Based, Meta-Analytic Appraisal of Environmental Enrichment Efficacy in Captive Primates

Non-human primates (hereafter 'primates') constitute a common group of animals in captivity but their captive maintenance involves ethical and husbandry issues, many of which can be addressed through environmental enrichment (hereafter 'enrichment'). Enrichment is often applied in a trial-and-error fashion or based on subjective assessments of efficacy. Thus, a predictive framework for enrichment is necessary to ensure it achieves the desired outcomes. As one of the initial steps towards the development of a predictive enrichment science, we aimed to identify the most effective enrichment approaches for captive primates. We conducted a comprehensive meta-analysis of the peer-reviewed literature and extracted information on methodological approaches, experimental design, species and environmental context. We developed and applied a novel efficacy index score to each study protocol as a comparable metric of enrichment efficacy in order to appraise current enrichment practices. Our findings suggest that captive primate enrichment approaches vary in their efficacy, with training-based enrichment being the most effective. Furthermore, the social context of subjects appears to influence efficacy, with primates housed alone deriving the most benefit from enrichment. A species' natural minimum group size may also influence enrichment efficacy but this relationship requires further investigation. Testing and reporting trends for captive primate enrichment are presented and discussed, highlighting important gaps in the literature and avenues of future research while identifying the beneficial effects of different enrichment practices.

Testing the 'parasite-mediated domestication' hypothesis: a comparative approach to the wild boar and domestic pig as model species

The mechanisms underlying the domestication process have already been well explained. Starting with Belyaev's pioneering experiment on silver foxes, which showed that selection for tameness (reduced fear response, changes in the 'hypothalamic-pituitary-adrenal system'-HPA axis) leads to destabilisation of the regulatory systems that control morphological and behavioural development, resulting in the changes characteristic of the domestication syndrome. Later, the thyroid rhythm hypothesis and the neural crest cell (NCC) hypothesis provided additional explanations. Recently, the parasite-mediated domestication hypothesis (PMD) has been proposed, suggesting an important role of endoparasites in the domestication process. Since parasites either directly or indirectly affect all mechanisms underlying the domestication syndrome (HPA, thyroid, NCC), the PMD proposes that they may be an important trigger of domestication. PMD can be tested either experimentally or comparatively. One of the basic assumptions of PMD is that parasite-susceptible, genetically less resistant/more tolerant wild animals were originally domesticated and that the susceptibility to parasites has been passed on to today's domestic animals. This can be verified primarily by comparing the parasite susceptibility of existing wild and domestic populations of the same species. We, therefore, followed a systematic comparative approach by analysing the parasite load in wild boar (WB) and free-ranging domestic pig (DP) populations from a comparable environment in a geographically close area. Fresh faeces from WB and DP populations, one each from Slovenia (SI) and Croatia (HR), were sampled. A total of 59 individual faecal samples were collected (SI: 12 WB, 20 DP; HR: 14 WB, 13 DP). Parasitological diagnostics were carried out using the sedimentation and floatation method. Five different taxa were found in WB and seven in DP. Three parasite taxa were found exclusively in DP (Cystoisospora suis, Trichuris sp., Balantidium coli), and one (Strongyloides sp.) only in WB. Of the parasites found in both cohorts, strongyles/Oesophagostomum sp. were significantly more abundant in DP, while Eimeria sp. was found in equal amounts in both (but in HR only in WB). According to the preliminary study presented here, there is evidence to support the PMD baselines in the wild boar-domestic pig association. However, we cannot draw a definitive conclusion as there are many aspects that may bias the interpretation based on parasite load alone, which are also discussed here. Therefore, comparative studies should be supported by a more focussed methodology, including an experimental approach.

Urbanization does not increase "object curiosity" in vervet monkeys, but semi-urban individuals selectively explore food-related anthropogenic items

Urban environments expose animals to abundant anthropogenic materials and foods that facilitate foraging innovations in species with opportunistic diets and high behavioral flexibility. Neophilia and exploration tendency are believed to be important behavioral traits for animals thriving in urban environments. Vervet monkeys (Chlorocebus pygerythrus) are one of few primate species that have successfully adapted to urban environments, thus making them an ideal species to study these traits. Using a within-species cross-habitat approach, we compared neophilia and exploration of novel objects (jointly referred to as "object curiosity") between semi-urban, wild, and captive monkeys to shed light on the cognitive traits facilitating urban living. To measure "object curiosity," we exposed monkeys to various types of novel stimuli and compared their approaches and explorative behavior. Our results revealed differences in the number of approaches and explorative behavior toward novel stimuli between the habitat types considered. Captive vervet monkeys were significantly more explorative than both semi- urban and wild troops, suggesting that positive experiences with humans and lack of predation, rather than exposure to human materials per se, influence object curiosity. Across habitats, juvenile males were the most explorative age-sex class. This is likely due to males being the dispersing sex and juveniles being more motivated to learn about their environment. Additionally, we found that items potentially associated with human food, elicited stronger explorative responses in semi-urban monkeys than non-food related objects, suggesting that their motivation to explore might be driven by "anthrophilia", that is, their experience of rewarding foraging on similar anthropogenic food sources. We conclude that varying levels of exposure to humans, predation and pre-exposure to human food packaging explain variation in "object curiosity" in our sample of vervet monkeys.

Perception of optical illusions in ungulates: insights from goats, sheep, guanacos and llamas

Optical illusions have long been used in behavioural studies to investigate the perceptual mechanisms underlying vision in animals. So far, three studies have focused on ungulates, providing evidence that they may be susceptible to some optical illusions, in a way similar to humans. Here, we used two food-choice tasks to study susceptibility to the Müller-Lyer and Delboeuf illusions in 17 captive individuals belonging to four ungulate species (Lama guanicoe, Lama glama, Ovis aries, Capra hircus). At the group level, there was a significant preference for the longer/larger food over the shorter/smaller one in control trials. Additionally, the whole group significantly preferred the food stick between two inward arrowheads over an identical one between two outward arrowheads in experimental trials of the Müller-Lyer task, and also preferred the food on the smaller circle over an identical one on the larger circle in the experimental trials of the Delboeuf task. Group-level analyses further showed no significant differences across species, although at the individual level we found significant variation in performance. Our findings suggest that, in line with our predictions, ungulates are overall susceptible to the Müller-Lyer and the Delboeuf illusions, and indicate that the perceptual mechanisms underlying size estimation in artiodactyls might be similar to those of other species, including humans.

Face masks in action: Birds show reduced fear responses to people wearing face masks during the COVID-19 pandemic in three Asian countries

The 2019 zoonotic pandemic (COVID-19), has led to a massive global lockdown that provides a good opportunity to study how wildlife responds to changes in human activity. Wearing a mask after the COVID-19 outbreak was widely used to prevent the spread of the causative pathogen. It has been shown that tree sparrows (Passer montanus) at two sites in south China exhibit reduced fear responses to people with face masks after a period of heavy exposure to them, whereas European studies showed the opposite, with no changes in the behaviour of the birds towards mask wearers in either rural or urban areas. To further study this, from October 2021 to January 2022, we conducted a flight initiation distance (FID) survey in Pakistan, Bangladesh, and Xi'an, China for a variety of field bird species by comparing the FID for researchers wearing masks to that for researchers not wearing masks to assess whether wearing masks in public places caused birds to adjust their flight response. Results from the three Asian countries showed that after a period of sustained contact with people wearing masks, in both rural and urban areas, birds were significantly more adapted to them and had a shorter FID to people wearing masks. We suggest that the rapid habituation of birds to people wearing masks with a reduced fear response could have some fitness advantage, allowing them to adapt rapidly to the new environmental conditions induced by COVID-19.

A bird's eye view of the hippocampus beyond space: Behavioral, neuroanatomical, and neuroendocrine perspectives

Although the hippocampus is one of the most-studied brain regions in mammals, research on the avian hippocampus has been more limited in scope. It is generally agreed that the hippocampus is an ancient feature of the amniote brain, and therefore homologous between the two lineages. Because birds and mammals are evolutionarily not very closely related, any shared anatomy is likely to be crucial for shared functions of their hippocampi. These functions, in turn, are likely to be essential if they have been conserved for over 300 million years. Therefore, research on the avian hippocampus can help us understand how this brain region evolved and how it has changed over evolutionary time. Further, there is a strong research foundation in birds on hippocampal-supported behaviors such as spatial navigation, food caching, and brood parasitism that scientists can build upon to better understand how hippocampal anatomy, network circuitry, endocrinology, and physiology can help control these behaviors. In this review, we summarize our current understanding of the avian hippocampus in spatial cognition as well as in regulating anxiety, approach-avoidance behavior, and stress responses. Although there are still some questions about the exact number of subdivisions in the avian hippocampus and how that might vary in different avian families, there is intriguing evidence that the avian hippocampus might have complementary functional profiles along the rostral-caudal axis similar to the dorsal-ventral axis of the rodent hippocampus, where the rostral/dorsal hippocampus is more involved in cognitive processes like spatial learning and the caudal/ventral hippocampus regulates emotional states, anxiety, and the stress response. Future research should focus on elucidating the cellular and molecular mechanisms - including endocrinological - in the avian hippocampus that underlie behaviors such as spatial navigation, spatial memory, and anxiety-related behaviors, and in so doing, resolve outstanding questions about avian hippocampal function and organization.

Conceptualization, context, and comparison are key to understanding the evolution of fear

The fearful ape hypothesis proposes that heightened fearfulness in humans is adaptive. However, despite its attractive anthropocentric narrative, the evidence presented for greater fearfulness in humans versus other apes is not sufficient to support this claim. Conceptualization, context, and comparison are strongly lacking in Grossmann's proposal, but are key to understanding variation in the fear response among individuals and species.

Innovation across 13 ungulate species: problem solvers are less integrated in the social group and less neophobic

Innovation is the ability to solve new problems or find novel solutions to familiar problems, and it is known to provide animals with crucial fitness benefits. Although this ability has been extensively studied in some taxa, the factors that predict innovation within and across species are still largely unclear. In this study, we used a novel foraging task to test 111 individuals belonging to 13 ungulate species-a still understudied taxon. To solve the task, individuals had to open transparent and opaque cups with food rewards, by removing their cover. We assessed whether individual factors (neophobia, social integration, sex, age, rank) and socio-ecological factors (dietary breadth, fission-fusion dynamics, domestication, group size) predicted participation and performance in the task. Using a phylogenetic approach, we showed that success was higher for less neophobic and socially less integrated individuals. Moreover, less neophobic individuals, individuals of domesticated species and having higher fission-fusion dynamics were more likely to participate in the task. These results are in line with recent literature suggesting a central role of sociality and personality traits to successfully deal with novel challenges, and confirm ungulates as a promising taxon to test evolutionary theories with a comparative approach.

Impacts of commingling preconditioned and auction-derived beef calves on bovine respiratory disease related morbidity, mortality, and weight gain

Introduction

Stressors predisposing to bovine respiratory disease (BRD) upon arrival in the feedlot, include the ranch to feedlot transition and mixing cattle from multiple sources. Preconditioning (PC) reduces multiple stressors, but commingling PC and auction-derived (AD) calves in a feedlot may increase BRD risk. Our objective was to evaluate PC calf performance over the first 40 days in the feedlot and determine impacts of commingling with varying proportions of AD calves (25, 50, and 75%).

Methods

Calves were either preconditioned at one ranch (n = 250) or mixed-source and bought from a local auction (n = 250). At arrival, calves were assigned into 1 of 5 pens: 100 PC, 75 PC, 50 PC, 25 PC, and 0 PC, reflecting the percentage of PC calves in a 100-head pen.

Results

Over 40 days, morbidity in pen 100 PC was lower compared to 0 PC (24 vs. 50%, P < 0.001) and varied in commingled pens, being highest (63%) in 25 PC and least (21%) in 50 PC (P < 0.05). There were 3 AD deaths in 0 PC and 2 deaths in 25 PC. The AD calves in 0 PC were 3 times more likely to get BRD than PC calves in 100 PC; however, AD calves gained 0.49 kg/d more than PC calves (P < 0.0001). Ignoring pen placement, AD calves were 2.76 times more likely to get BRD but gained 0.27 kg/d more than PC calves (P < 0.0001). Commingling did not affect morbidity of PC (P = 0.5) or AD calves (P = 0.96), implying commingling did not affect health. Calves in 25 PC were 3.39 times more likely to get BRD than those in the 100 PC (P < 0.001). Furthermore, 25 PC calves gained the most (1.08 kg/d), followed by 50 PC (0.62 kg/d) and 75 PC (0.61 kg/d), compared to 100 PC (P < 0.05). Calf weight at arrival modified ADG (P < 0.05).

Discussion

In conclusion, PC calves had lower morbidity over the first 40 days, irrespective of commingling. With larger variations in arrival weight, there was no advantage of PC for ADG in the first 40 days. The unknown weaning strategies and comparable arrival weights of AD calves may have contributed to greater ADG in AD calves.

Fear of the new? Geckos hesitate to attack novel prey, feed near objects and enter a novel space

Neophobia, the fear of novelty, is an ecologically important response which enables animals to avoid potentially harmful situations. Neophobia is a cognitive process by which individuals distinguish novelty from familiarity. In this study, we aimed to quantify this cognitive process in captive tokay geckos (Gekko gecko) across three contexts: when encountering novel prey, foraging near novel objects and entering a novel space. We also investigated individual consistency across trials using different novel stimuli, and correlation of individual responses across the three contexts. We found that geckos hesitate to attack novel prey and prey close to objects (familiar and novel). Geckos hesitated the most when entering novel space. Repeatability of behaviour within and across contexts was low (R = 0.101-0.190) indicating that neophobia might not be expressed similarly across contexts. The strength of a neophobic response can indicate how anxious or curious an individual is. This test has great potential to help answer questions about how captivity, enrichment, rearing environment and cognition affect fear responses in different contexts in lizards. By studying reptiles, we can better understand the universality of what is known about the causes leading to difference in neophobia across individuals and species.

Carbohydrate pellets to assess insulin dysregulation in horses

BACKGROUND

A glycemic challenge test is used for the diagnosis of insulin dysregulation (ID) in horses and ponies. Different forms of the test exist where the administrative route and dose of glucose vary, which makes interpretation of results challenging.

HYPOTHESIS/OBJECTIVES

To evaluate the palatability of, and blood glucose and insulin responses to, carbohydrate pellets fed as an oral glucose test (OGT), and to establish the diagnostic threshold for ID when using the pellets.

ANIMALS

University and privately-owned horses and ponies (n = 157) comprised of 31 breeds and both sexes.

METHODS

Multicenter cohort study. A custom-produced glycemic pellet was offered for free intake at 0.5 g/kg BW soluble carbohydrate and serum insulin and blood glucose concentrations measured before and after (60, 120, and 180 minutes) the pellets were offered. Pellet acceptance and intake time (those that finished within 10 minutes) were determined to assess palatability.

RESULTS

The pellets were palatable to 132/157 animals, and ponies found the pellets more (P = .004) palatable than horses. The median intake time (4 [3-6] minutes) was positively correlated with acceptance grade (r = .51; P < .0001). Consumption of the pellets elicited peak blood glucose (6.6 [5.8-7.8] mmol/L) and serum insulin (40.5 [19-99.8] μIU/mL) responses at 120 minutes. At 120 minutes the optimal cut-off was 83 μIU/mL (95% CI: 70-99 μIU/mL) for the IMMULITE 2000XPi assay.

CONCLUSIONS AND CLINICAL IMPORTANCE

The pellets were palatable and a suitable, novel carbohydrate source for the OGT.

Horses’ Response to a Novel Diet: Different Herbs Added to Dry, Wet or Wet-Sweetened Oats

Simple Summary

The commercial horse feed industry uses palatants to mask undesirable tastes of feed and enhance consumption. However, an unknown smell or taste may also hinder feed intake, due to, among other aspects, novelty. The acceptability of herbs by horses has not been studied. We analysed whether five herbs (field mint, common yarrow, common chamomile, common sage and common nettle) added alternately to oats and presented within a dry, wet or wet-sweetened diet influence horses’ willingness to consume. Twenty horses were given different diet combinations of a feed presentation and a herb consecutively, once daily. Seven parameters showing the willingness to consume were measured: times of olfaction and consumption, times and numbers of intervals in consumption and drinking water, and mass of leftovers. The results show that the herbs in the amount offered did not influence the time of intake and only the dry oats with common sage added were smelled longer before consuming. However, wetting or wetting and sweetening the feed increased the willingness to eat. In conclusion, herbs in small amounts do not affect the feed intake, whereas wetting and sweetening the diet is of great importance and should be regarded when preparing horse diets.

Abstract

The commercial horse feed industry uses palatants to mask undesirable tastes of feeds and enhance product acceptance. However, an unknown odour or taste may also hinder feed intake, due to, inter alia, novelty. The objective of the study was to assess the horses’ response to novel diet: five different herbs added alternately to dry, wet or wet-sweetened oats. Twenty adult horses were given different diet combinations of a feed presentation and a herb: field mint, common yarrow, common chamomile, common sage and common nettle, consecutively, once daily. The response to novelty was assessed regarding traits showing the willingness to consume: times of olfaction and consumption, times and numbers of intervals in consumption and drinking water, and the mass of leftovers. The results show that properties of the herbs studied did not hinder the consumption and only the odour of the dry common sage delayed the intake. Wetting or wetting and sweetening the diet accelerated the intake. In conclusion, herbs in small amounts do not significantly affect the willingness to consume feed. Although wet and wet-sweetened diet presentations may be novel to horses, they increase the feed palatability and can be suggested for use when preparing horse diets.

Exploring innovative problem-solving in African lions (Panthera leo) and snow leopards (Panthera uncia)

Cognitive ability is likely linked to adaptive ability; animals use cognition to innovate and problem-solve in their physical and social environments. We investigated innovative problem-solving in two species of high conservation importance: African lions (Panthera leo; n = 6) and snow leopards (Panthera uncia; n = 9). We designed a custom multi-access puzzle box (MAB) to present a simple and effective behavioral test for the cats to explore. We measured Repeated Innovation, Persistence, Success, Contact Latency, and the Exploration Diversity of individuals interacting with the MAB. Of the six African lions, three (50%) solved one door to the box, one solved two doors (16.67%), and one solved three doors (16.67%). Of the nine snow leopards, one solved one door (11.11%), three solved two doors (33.33%), and none solved all three doors (0%). Persistence was a significant predictor of Success in African lions and snow leopards; more Persistent individuals were more likely to open a door. We also observed significant individual variation in Persistence for both species, but only snow leopards also exhibited differences in Contact Latency and Exploration Diversity. These results suggest individuals vary in their problem-solving approaches. Our findings support both species as successful, repeated innovators. Carnivores face ecological and social challenges and, presumably, benefit from cognitive abilities facilitating the successful navigation of these challenges in captivity and the wild.

Individual Variation in Response to Novel Food in Captive Capuchin Monkeys (Sapajus spp.)

How animals respond to novelty may have important outcomes in terms of fitness. On the one hand, aversion to novel stimuli may reduce the risks of consuming potentially toxic food or encountering predators. On the other hand, the propensity to approach novel stimuli may allow individuals to explore novel food sources and more flexibly adapt to novel challenges. Different species and individuals may find different ways to balance the costs and benefits that novelty posits. To date, however, little is known on how response to novel food varies across individuals of the same species depending on their previous experience with novelty, risk attitude and presence of higher-ranking conspecifics. In this study, we assessed individual variation in response to novel food by testing captive capuchin monkeys (Sapajus spp.) in an unconstrained social context, where all individuals in a group were able to access the testing area on a voluntary basis. We provided familiar and novel food to 23 study subjects belonging to four social groups differing in (i) previous experience with novel food, (ii) risk attitude (as assessed by a previous risky decision-making task), and (iii) dominance rank. We predicted that, as individuals may generalize their previous experience to novel contexts, those with more previous experience with novel food would be less neophobic than those with less experience. Moreover, if neophobia is a facet of the individual’s risk attitude, we predicted that more risk-prone individuals would be less neophobic than less risk-prone ones. Finally, individuals might flexibly modify their food choices according to the presence of conspecifics; in this respect, we predicted that, in response to monopolization of preferred resources by higher-ranking individuals, lower-ranking individuals would prefer familiar over novel food in the absence of higher-ranking individuals, but would modify their preference in favor of novel food in the presence of higher-ranking individuals. None of these predictions were supported by our results. We observed, however, that neophobia, measured as the latency to retrieve a food item, was more pronounced in lower-ranking than higher-ranking individuals, and that males showed a generally stronger bias than females toward a quicker retrieval of familiar food.

Socio-ecological correlates of neophobia in corvids

Behavioral responses to novelty, including fear and subsequent avoidance of novel stimuli, i.e., neophobia, determine how animals interact with their environment. Neophobia aids in navigating risk and impacts on adaptability and survival. There is variation within and between individuals and species; however, lack of large-scale, comparative studies critically limits investigation of the socio-ecological drivers of neophobia. In this study, we tested responses to novel objects and food (alongside familiar food) versus a baseline (familiar food alone) in 10 corvid species (241 subjects) across 10 labs worldwide. There were species differences in the latency to touch familiar food in the novel object and novel food conditions relative to the baseline. Four of seven socio-ecological factors influenced object neophobia: (1) use of urban habitat (versus not), (2) territorial pair versus family group sociality, (3) large versus small maximum flock size, and (4) moderate versus specialized caching (whereas range, hunting live animals, and genus did not), while only maximum flock size influenced food neophobia. We found that, overall, individuals were temporally and contextually repeatable (i.e., consistent) in their novelty responses in all conditions, indicating neophobia is a stable behavioral trait. With this study, we have established a network of corvid researchers, demonstrating potential for further collaboration to explore the evolution of cognition in corvids and other bird species. These novel findings enable us, for the first time in corvids, to identify the socio-ecological correlates of neophobia and grant insight into specific elements that drive higher neophobic responses in this avian family group. VIDEO ABSTRACT.

Anti Covid-19 face-masks increases vigilance in Nubian ibex (Capra nubiana)

Changes in ecosystems resulting from anthropause caused by Covid-19 relate to both abiotic and biotic factors which have both a positive or negative effect on wildlife. The lockdown was manifested by reduced air and water pollution, lower mortality of animals on the roads, an increase in animals' body condition and reproduction success. On the other hand, the closures lead to an increase in the populations of invasive species or poaching. We studied the behavioural reaction of natural, desert-dwelling Nubian ibex (Capra nubiana) on the appearance of a new element in the environment - the facial-masks. We hypothesized that the mask would trigger a response expressed through differences in the vigilance towards a potentially new threat. We applied the flight initiation distance (FID) technique to check the reaction at the approach of a human with a facial-mask and without it. The average FID was 8.8 m and was longer when the observer was wearing a mask (10.7 m) as compared to trials without the mask (6.9 m). Our study indicates that wildlife, even if habituated to human silhouette at a distance, appear to notice unusual accessories when up-close and respond by increased vigilance and what may affect their overall fitness.