Weevil x Insecticide: Does ‘Personality’ Matter?

An insect’s behavior is the expression of its integrated physiology in response to external and internal stimuli, turning insect behavior into a potential determinant of insecticide exposure. Behavioral traits may therefore influence insecticide efficacy against insects, compromising the validity of standard bioassays of insecticide activity, which are fundamentally based on lethality alone. By extension, insect ‘personality’ (i.e., an individual’s integrated set of behavioral tendencies that is inferred from multiple empirical measures) may also be an important determinant of insecticide exposure and activity. This has yet to be considered because the behavioral studies involving insects and insecticides focus on populations rather than on individuals. Even among studies of animal ‘personality’, the relative contributions of individual and population variation are usually neglected. Here, we assessed behavioral traits (within the categories: activity, boldness/shyness, and exploration/avoidance) of individuals from 15 populations of the maize weevil (Sitophilus zeamais), an important stored-grain pest with serious problems of insecticide resistance, and correlated the behavioral responses with the activity of the insecticide deltamethrin. This analysis was performed at both the population and individual levels. There was significant variation in weevil ‘personality’ among individuals and populations, but variation among individuals within populations accounted for most of the observed variation (92.57%). This result emphasizes the importance of individual variation in behavioral and ‘personality’ studies. When the behavioral traits assessed were correlated with median lethal time (LT₅₀) at the population level and with the survival time under insecticide exposure, activity traits, particularly the distance walked, significantly increased survival time. Therefore, behavioral traits are important components of insecticide efficacy, and individual variation should be considered in such studies. This is so because population differences provided only crude approximation of the individual personality in a restrained experimental setting likely to restrict individual behavior favoring the transposition of the individual variation to the population.     

Odour cues from suitors’ nests determine mating success in a fish

Animals use a range of sensory cues for finding food, avoiding predators and choosing mates. In this regard, the aquatic environment is particularly suitable for the use of olfactory and other chemical cues. Nevertheless, mate choice research, even on aquatic organisms, has focused on visual signals, while chemical cues relevant in sexual selection have been assumed to be ‘intrinsic’ excretions of mate candidates. Here, using the sand goby Pomatoschistus minutus, a small fish with paternal egg care, we investigated the possibility that ‘extrinsic’ chemical cues in the males’ nests could also have a significant contribution to mating success. We found that females strongly avoided laying eggs into nests subject to the odour of Saprolegnia water moulds (an egg infection) and that this effect was independent of the females’ initial, visually based preference for males. To the best of our knowledge, this is the first study to show that chemical cues related to parental failure can play a large role in sexual selection.     

Invasive Cane Toads: Social Facilitation Depends upon an Individual’s Personality

Individual variation in behavioural traits (including responses to social cues) may influence the success of invasive populations. We studied the relationship between sociality and personality in invasive cane toads (Rhinella marina) from a recently established population in tropical Australia. In our field experiments, we manipulated social cues (the presence of a feeding conspecific) near a food source. We captured and compared toads that only approached feeding sites where another toad was already present, with conspecifics that approached unoccupied feeding sites. Subsequent laboratory trials showed correlated personality differences (behavioural syndromes) between these two groups of toads. For example, toads that approached already-occupied rather than unoccupied feeding sites in the field, took longer to emerge from a shelter-site in standardized trials, suggesting these individuals are ‘shy’ (whereas toads that approached unoccupied feeding stations tended to be ‘bold’). Manipulating hunger levels did not abolish this difference. In feeding trials, a bold toad typically outcompeted a shy toad under conditions of low prey availability, but the outcome was reversed when multiple prey items were present. Thus, both personality types may be favored under different circumstances. This invasive population of toads contains individuals that exhibit a range of personalities, hinting at the existence of a wide range of social dynamics in taxa traditionally considered to be asocial.     

Baby on board: olfactory cues indicate pregnancy and fetal sex in a non-human primate

Olfactory cues play an integral, albeit underappreciated, role in mediating vertebrate social and reproductive behaviour. These cues fluctuate with the signaller''s hormonal condition, coincident with and informative about relevant aspects of its reproductive state, such as pubertal onset, change in season and, in females, timing of ovulation. Although pregnancy dramatically alters a female''s endocrine profiles, which can be further influenced by fetal sex, the relationship between gestation and olfactory cues is poorly understood. We therefore examined the effects of pregnancy and fetal sex on volatile genital secretions in the ring-tailed lemur (Lemur catta), a strepsirrhine primate possessing complex olfactory mechanisms of reproductive signalling. While pregnant, dams altered and dampened their expression of volatile chemicals, with compound richness being particularly reduced in dams bearing sons. These changes were comparable in magnitude with other, published chemical differences among lemurs that are salient to conspecifics. Such olfactory ‘signatures’ of pregnancy may help guide social interactions, potentially promoting mother–infant recognition, reducing intragroup conflict or counteracting behavioural mechanisms of paternity confusion; cues that also advertise fetal sex may additionally facilitate differential sex allocation.     

Smelling wrong: hormonal contraception in lemurs alters critical female odour cues

Animals, including humans, use olfaction to assess potential social and sexual partners. Although hormones modulate olfactory cues, we know little about whether contraception affects semiochemical signals and, ultimately, mate choice. We examined the effects of a common contraceptive, medroxyprogesterone acetate (MPA), on the olfactory cues of female ring-tailed lemurs (Lemur catta), and the behavioural response these cues generated in male conspecifics. The genital odorants of contracepted females were dramatically altered, falling well outside the range of normal female variation: MPA decreased the richness and modified the relative abundances of volatile chemicals expressed in labial secretions. Comparisons between treatment groups revealed several indicator compounds that could reliably signal female reproductive status to conspecifics. MPA also changed a female''s individual chemical ‘signature’, while minimizing her chemical distinctiveness relative to other contracepted females. Most remarkably, MPA degraded the chemical patterns that encode honest information about genetic constitution, including individual diversity (heterozygosity) and pairwise relatedness to conspecifics. Lastly, males preferentially investigated the odorants of intact over contracepted females, clearly distinguishing those with immediate reproductive potential. By altering the olfactory cues that signal fertility, individuality, genetic quality and relatedness, contraceptives may disrupt intraspecific interactions in primates, including those relevant to kin recognition and mate choice.     

Antarctic Climate Change: Extreme Events Disrupt Plastic Phenotypic Response in Adélie Penguins

In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins (Pygoscelis adeliae) breeding in the Ross Sea. A ‘natural experiment’ brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The ‘natural experiment’ uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise.     

Flying bats use serial sampling to locate odour sources

Olfactory tracking generally sacrifices speed for sensitivity, but some fast-moving animals appear surprisingly efficient at foraging by smell. Here, we analysed the olfactory tracking strategies of flying bats foraging for fruit. Fruit- and nectar-feeding bats use odour cues to find food despite the sensory challenges derived from fast flight speeds and echolocation. We trained Jamaican fruit-eating bats (Artibeus jamaicensis) to locate an odour reward and reconstructed their flight paths in three-dimensional space. Results confirmed that bats relied upon olfactory cues to locate a reward. Flight paths revealed a combination of odour- and memory-guided search strategies. During ‘inspection flights’, bats significantly reduced flight speeds and flew within approximately 6 cm of possible targets to evaluate the presence or absence of the odour cue. This behaviour combined with echolocation explains how bats maximize foraging efficiency while compensating for trade-offs associated with olfactory detection and locomotion.     

Fasting for 24 Hours Heightens Reward from Food and Food-Related Cues

Introduction

We examined the impact of a 24 hour complete fast (vs. fed state) on two measures of food reward: 1) ‘wanting’, as measured by response to food images and by the relative-reinforcing value of food (RRV), and 2) ‘liking’, as measured by response to food images and the hedonic evaluation of foods consumed.

Methods

Utilizing a randomized crossover design, 15 subjects (9 male; 6 female) aged 28.6±4.5 yrs with body mass index 25.3±1.4 kg/m² were randomized and counterbalanced to normal feeding (FED) and 24-hour fast (FASTED) conditions. Trait characteristics were measured with the Three Factor Eating Questionnaire. Two computer tasks measured food reward: 1) RRV progressive ratio task, 2) explicit ‘liking’ and ‘wanting’ (Leeds Food Preference Questionnaire, LFPQ). Also measured were ad libitum energy intake (EI; buffet) and food ‘liking’ (visual analogue scale) of personalized stimuli.

Results

There were no significant anthropometric changes between conditions. Appetite scores, hedonic ratings of ‘liking’, and ad libitum EI all significantly increased under the FASTED condition (p<0.05). Under the FASTED condition there were significant increases in the RRV of snack foods; similarly, explicit ‘wanting’ and ‘liking’ significantly increased for all food categories. ‘Liking’ of sweet foods remained high across-meals under FASTED, but savory foods decreased in hedonic saliency.

Conclusion

Relative to a fed state, we observed an increase in hedonic ratings of food, the rewarding value of food, and food intake after a 24 hr fast. Alliesthesia to food and food cues is suggested by heightened hedonic ratings under the FASTED condition relative to FED.     

The Obesogenic Quality of the Home Environment: Associations with Diet,Physical Activity,TV Viewing,and BMI in Preschool Children

Objectives

The home environment is thought to play a key role in early weight trajectories, although direct evidence is limited. There is general agreement that multiple factors exert small individual effects on weight-related outcomes, so use of composite measures could demonstrate stronger effects. This study therefore examined whether composite measures reflecting the ‘obesogenic’ home environment are associated with diet, physical activity, TV viewing, and BMI in preschool children.

Methods

Families from the Gemini cohort (n = 1096) completed a telephone interview (Home Environment Interview; HEI) when their children were 4 years old. Diet, physical activity, and TV viewing were reported at interview. Child height and weight measurements were taken by the parents (using standard scales and height charts) and reported at interview. Responses to the HEI were standardized and summed to create four composite scores representing the food (sum of 21 variables), activity (sum of 6 variables), media (sum of 5 variables), and overall (food composite/21 + activity composite/6 + media composite/5) home environments. These were categorized into ‘obesogenic risk’ tertiles.

Results

Children in ‘higher-risk’ food environments consumed less fruit (OR; 95% CI = 0.39; 0.27–0.57) and vegetables (0.47; 0.34–0.64), and more energy-dense snacks (3.48; 2.16–5.62) and sweetened drinks (3.49; 2.10–5.81) than children in ‘lower-risk’ food environments. Children in ‘higher-risk’ activity environments were less physically active (0.43; 0.32–0.59) than children in ‘lower-risk’ activity environments. Children in ‘higher-risk’ media environments watched more TV (3.51; 2.48–4.96) than children in ‘lower-risk’ media environments. Neither the individual nor the overall composite measures were associated with BMI.

Conclusions

Composite measures of the obesogenic home environment were associated as expected with diet, physical activity, and TV viewing. Associations with BMI were not apparent at this age.     

Sexual deception in a cannibalistic mating system? Testing the Femme Fatale hypothesis

Animal communication theory holds that in order to be evolutionarily stable, signals must be honest on average, but significant dishonesty (i.e. deception) by a subset of the population may also evolve. A typical praying mantid mating system involves active mate searching by males, which is guided by airborne sex pheromones in most species for which mate-searching cues have been studied. The Femme Fatale hypothesis suggests that female mantids may be selected to exploit conspecific males as prey if they benefit nutritionally from cannibalism. Such a benefit exists in the false garden mantid Pseudomantis albofimbriata—females use the resources gained from male consumption to significantly increase their body condition and reproductive output. This study aimed to examine the potential for chemical deception among the subset of females most likely to benefit from cannibalism (poorly fed females). Females were placed into one of four feeding treatments (‘Very Poor’, ‘Poor’, ‘Medium’ and ‘Good’), and males were given the opportunity to choose between visually obscured females in each of the treatments. Female body condition and fecundity varied linearly with food quantity; however, female attractiveness did not. That is, Very Poor females attracted significantly more males than any of the other female treatments, even though these females were in significantly poorer condition, less fecund (in this study) and more likely to cannibalise (in a previous study). In addition, there was a positive correlation between fecundity and attractiveness if Very Poor females were removed from the analysis, suggesting an inherently honest signalling system with a subset of dishonest individuals. This is the first empirical study to provide evidence of sexual deception via chemical cues, and the first to provide support for the Femme Fatale hypothesis.     

Further Explorations of the Facing Bias in Biological Motion Perception: Perspective Cues,Observer Sex,and Response Times

The human visual system has evolved to be highly sensitive to visual information about other persons and their movements as is illustrated by the effortless perception of point-light figures or ‘biological motion’. When presented orthographically, a point-light walker is interpreted in two anatomically plausible ways: As ‘facing the viewer’ or as ‘facing away’ from the viewer. However, human observers show a ‘facing bias’: They perceive such a point-light walker as facing towards them in about 70-80% of the cases. In studies exploring the role of social and biological relevance as a possible account for the facing bias, we found a ‘figure gender effect’: Male point-light figures elicit a stronger facing bias than female point-light figures. Moreover, we also found an ‘observer gender effect’: The ‘figure gender effect’ was stronger for male than for female observers. In the present study we presented to 11 males and 11 females point-light walkers of which, very subtly, the perspective information was manipulated by modifying the earlier reported ‘perspective technique’. Proportions of ‘facing the viewer’ responses and reaction times were recorded. Results show that human observers, even in the absence of local shape or size cues, easily pick up on perspective cues, confirming recent demonstrations of high visual sensitivity to cues on whether another person is potentially approaching. We also found a consistent difference in how male and female observers respond to stimulus variations (figure gender or perspective cues) that cause variations in the perceived in-depth orientation of a point-light walker. Thus, the ‘figure gender effect’ is possibly caused by changes in the relative locations and motions of the dots that the perceptual system tends to interpret as perspective cues. Third, reaction time measures confirmed the existence of the facing bias and recent research showing faster detection of approaching than receding biological motion.     

A foraging advantage for dichromatic marmosets (Callithrix geoffroyi) at low light intensity

Most New World monkey species have both dichromatic and trichromatic individuals present in the same population. The selective forces acting to maintain the variation are hotly debated and are relevant to the evolution of the ‘routine’ trichromatic colour vision found in catarrhine primates. While trichromats have a foraging advantage for red food compared with dichromats, visual tasks which dichromats perform better have received less attention. Here we examine the effects of light intensity on foraging success among marmosets. We find that dichromats outperform trichomats when foraging in shade, but not in sun. The simplest explanation is that dichromats pay more attention to achromatic cues than trichromats. However, dichromats did not show a preference for foraging in shade compared with trichromats. Our results reveal several interesting parallels with a recent study in capuchin monkeys (Cebus capucinus), and suggest that dichromat advantage for certain tasks contributes to maintenance of the colour vision polymorphism.     

High Levels of Heterogeneity in the HIV Cascade of Care across Different Population Subgroups in British Columbia,Canada

Background

The HIV cascade of care (cascade) is a comprehensive tool which identifies attrition along the HIV care continuum. We executed analyses to explicate heterogeneity in the cascade across key strata, as well as identify predictors of attrition across stages of the cascade.

Methods

Using linked individual-level data for the population of HIV-positive individuals in BC, we considered the 2011 calendar year, including individuals diagnosed at least 6 months prior, and excluding individuals that died or were lost to follow-up before January 1^st, 2011. We defined five stages in the cascade framework: HIV ‘diagnosed’, ‘linked’ to care, ‘retained’ in care, ‘on HAART’ and virologically ‘suppressed’. We stratified the cascade by sex, age, risk category, and regional health authority. Finally, multiple logistic regression models were built to predict attrition across each stage of the cascade, adjusting for stratification variables.

Results

We identified 7621 HIV diagnosed individuals during the study period; 80% were male and 5% were <30, 17% 30–39, 37% 40–49 and 40% were ≥50 years. Of these, 32% were MSM, 28% IDU, 8% MSM/IDU, 12% heterosexual, and 20% other. Overall, 85% of individuals ‘on HAART’ were ‘suppressed’; however, this proportion ranged from 60%–93% in our various stratifications. Most individuals, in all subgroups, were lost between the stages: ‘linked’ to ‘retained’ and ‘on HAART’ to ‘suppressed’. Subgroups with the highest attrition between these stages included females and individuals <30 years (regardless of transmission risk group). IDUs experienced the greatest attrition of all subgroups. Logistic regression results found extensive statistically significant heterogeneity in attrition across the cascade between subgroups and regional health authorities.

Conclusions

We found that extensive heterogeneity in attrition existed across subgroups and regional health authorities along the HIV cascade of care in B.C., Canada. Our results provide critical information to optimize engagement in care and health service delivery.     

Genetic composition of social groups influences male aggressive behaviour and fitness in natural genotypes of Drosophila melanogaster

Indirect genetic effects (IGEs) describe how an individual''s behaviour—which is influenced by his or her genotype—can affect the behaviours of interacting individuals. IGE research has focused on dyads. However, insights from social networks research, and other studies of group behaviour, suggest that dyadic interactions are affected by the behaviour of other individuals in the group. To extend IGE inferences to groups of three or more, IGEs must be considered from a group perspective. Here, I introduce the ‘focal interaction’ approach to study IGEs in groups. I illustrate the utility of this approach by studying aggression among natural genotypes of Drosophila melanogaster. I chose two natural genotypes as ‘focal interactants’: the behavioural interaction between them was the ‘focal interaction’. One male from each focal interactant genotype was present in every group, and I varied the genotype of the third male—the ‘treatment male’. Genetic variation in the treatment male''s aggressive behaviour influenced the focal interaction, demonstrating that IGEs in groups are not a straightforward extension of IGEs measured in dyads. Further, the focal interaction influenced male mating success, illustrating the role of IGEs in behavioural evolution. These results represent the first manipulative evidence for IGEs at the group level.     

Individual boldness is linked to protective shell shape in aquatic snails

The existence of consistent individual differences in behaviour (‘animal personality’) has been well documented in recent years. However, how such individual variation in behaviour is maintained over evolutionary time is an ongoing conundrum. A well-studied axis of animal personality is individual variation along a bold–shy continuum, where individuals differ consistently in their propensity to take risks. A predation-risk cost to boldness is often assumed, but also that the reproductive benefits associated with boldness lead to equivalent fitness outcomes between bold and shy individuals over a lifetime. However, an alternative or complementary explanation may be that bold individuals phenotypically compensate for their risky lifestyle to reduce predation costs, for instance by investing in more pronounced morphological defences. Here, we investigate the ‘phenotypic compensation’ hypothesis, i.e. that bold individuals exhibit more pronounced anti-predator defences than shy individuals, by relating shell shape in the aquatic snail Radix balthica to an index of individual boldness. Our analyses find a strong relationship between risk-taking propensity and shell shape in this species, with bolder individuals exhibiting a more defended shell shape than shy individuals. We suggest that this supports the ‘phenotypic compensation’ hypothesis and sheds light on a previously poorly studied mechanism to promote the maintenance of personality variation among animals.     

Host–parasite interactions: resist or tolerate but never stop running

A conference exploring ‘The impact of the environment on innate immunity: the threat of diseases’ was held on 4–9 May 2009 in Obergurgl, Austria, thanks to the support from the European Science Foundation, Innsbruck University and the Austrian Science Foundation. The goals of the conference were to explore how the outcomes of host–parasite interactions depend on variation across individuals, their parasites and the environment in which they both find themselves. Central themes were the inherent costs of mounting an immune response, the ability of some organisms to pre-empt infection by ‘priming’ their immune systems, the fact that parasites learn to evade immune responses over time and the use of theory to predict when diseases will get out of hand. Many of the systems presented had clear impacts on human health, agriculture or the maintenance of complex ecosystems. There was common ground throughout in developing methodologies and embracing what one of the organizers termed the ‘interactome’ between hosts and those which would exploit them.     

How Skill Expertise Shapes the Brain Functional Architecture: An fMRI Study of Visuo-Spatial and Motor Processing in Professional Racing-Car and Na?ve Drivers

The present study was designed to investigate the brain functional architecture that subserves visuo-spatial and motor processing in highly skilled individuals. By using functional magnetic resonance imaging (fMRI), we measured brain activity while eleven Formula racing-car drivers and eleven ‘naïve’ volunteers performed a motor reaction and a visuo-spatial task. Tasks were set at a relatively low level of difficulty such to ensure a similar performance in the two groups and thus avoid any potential confounding effects on brain activity due to discrepancies in task execution. The brain functional organization was analyzed in terms of regional brain response, inter-regional interactions and blood oxygen level dependent (BOLD) signal variability. While performance levels were equal in the two groups, as compared to naïve drivers, professional drivers showed a smaller volume recruitment of task-related regions, stronger connections among task-related areas, and an increased information integration as reflected by a higher signal temporal variability. In conclusion, our results demonstrate that, as compared to naïve subjects, the brain functional architecture sustaining visuo-motor processing in professional racing-car drivers, trained to perform at the highest levels under extremely demanding conditions, undergoes both ‘quantitative’ and ‘qualitative’ modifications that are evident even when the brain is engaged in relatively simple, non-demanding tasks. These results provide novel evidence in favor of an increased ‘neural efficiency’ in the brain of highly skilled individuals.     

Lunar rhythms in growth of larval fish

Growth and survival of larval fishes is highly variable and unpredictable. Our limited understanding of this variation constrains our ability to forecast population dynamics and effectively manage fisheries. Here we show that daily growth rates of a coral reef fish (the sixbar wrasse, Thalassoma hardwicke) are strongly lunar-periodic and predicted by the timing of nocturnal brightness: growth was maximized when the first half of the night was dark and the second half of the night was bright. Cloud cover that obscured moonlight facilitated a ‘natural experiment’, and confirmed the effect of moonlight on growth. We suggest that lunar-periodic growth may be attributable to light-mediated suppression of diel vertical migrations of predators and prey. Accounting for such effects will improve our capacity to predict the future dynamics of marine populations, especially in response to climate-driven changes in nocturnal cloud cover and intensification of artificial light, which could lead to population declines by reducing larval survival and growth.     

Speed and accuracy in nest-mate recognition: a hover wasp prioritizes face recognition over colony odour cues to minimize intrusion by outsiders

Social insects have evolved sophisticated recognition systems enabling them to accept nest-mates but reject alien conspecifics. In the social wasp, Liostenogaster flavolineata (Stenogastrinae), individuals differ in their cuticular hydrocarbon profiles according to colony membership; each female also possesses a unique (visual) facial pattern. This species represents a unique model to understand how vision and olfaction are integrated and the extent to which wasps prioritize one channel over the other to discriminate aliens and nest-mates. Liostenogaster flavolineata females are able to discriminate between alien and nest-mate females using facial patterns or chemical cues in isolation. However, the two sensory modalities are not equally efficient in the discrimination of ‘friend’ from ‘foe’. Visual cues induce an increased number of erroneous attacks on nest-mates (false alarms), but such attacks are quickly aborted and never result in serious injury. Odour cues, presented in isolation, result in an increased number of misses: erroneous acceptances of outsiders. Interestingly, wasps take the relative efficiencies of the two sensory modalities into account when making rapid decisions about colony membership of an individual: chemical profiles are entirely ignored when the visual and chemical stimuli are presented together. Thus, wasps adopt a strategy to ‘err on the safe side’ by memorizing individual faces to recognize colony members, and disregarding odour cues to minimize the risk of intrusion from colony outsiders.     

Does Trapping Influence Decision-Making under Ambiguity in White-Lipped Peccary (Tayassu pecari)?

The white-lipped peccary (Tayassu pecari) is an endangered species whose bold anti-predator behaviour in comparison to related species may increase its vulnerability to hunting and predation. We used a judgement bias test to investigate whether captive peccaries that had recently experienced a trapping event made more ‘pessimistic’ decisions under ambiguity. If so, this would indicate (i) that the procedure may induce a negative affective state and hence have welfare implications, and (ii) that the species is able to adopt a cautious response style despite its bold phenotype. Eight individuals were trained to ‘go’ to a baited food bowl when a positive auditory cue (whistle; CS+) was given and to ‘no-go’ when a negative cue (horn A; CS-) was sounded to avoid a loud sound and empty food bowl. An ‘ambiguous’ auditory cue (bell; CSA) was presented to probe decision-making under ambiguity. Individuals were subjected to three tests in the order: T1 (control-no trap), T2 (24h after-trap procedure), and T3 (control-no trap). In each test, each animal was exposed to 10 judgement bias trials of each of the three cue types: CS+,CS-,CS_A. We recorded whether animals reached the food bowl within 60s (‘go’ response) and their response speed (m/s). The animals varied in their responses to the CS_A cue depending on test type. In all tests, animals made more ‘go’ responses to CS+ than CS_A. During control tests (T1 and T3), the peccaries showed higher proportions of ‘go’ responses to CS_A than to CS-. In T2, however, the animals showed similar proportions of ‘go’ responses to CS_A and CS-, treating the ambiguous cue similarly to the negative cue. There were differences in their response speed according to cue type: peccaries were faster to respond to CS+ than to CS- and CS_A. Trapping thus appeared to cause a ‘pessimistic’ judgement bias in peccaries, which may reflect a negative affective state with implications for the welfare and management of captive individuals, and also function to increase caution and survival chances following such an event in the wild environment.