Measurement of cognitive bias and cortisol levels to evaluate the effects of space restriction on captive collared peccary (Mammalia, Tayassuidae)

Abstract

a b s t r a c tWe use the judgement-bias paradigm to evaluate whether space restriction in metabolism pens affects the emotional state of collared peccary (Pecari tajacu) during a nutritional experiment. We trained individual adult males to 'go' to a specific location within 30 s when a positive auditory cue (whistle; CS+) was given in order to receive cassava root pieces as a reward, and to 'no-go' when a negative cue (caxixi percussion instrument; CS−) was sounded to avoid punishment (jet of water) and no reward. An 'ambiguous' auditory cue (a drumstick hitting an aluminum plate; CS A ) was presented to probe decision-making under ambiguity. Individuals were subjected to five 8-day housing conditions in the order: H1 (controlno space restriction-metabolism pen and additional area), H2 space restriction without environmental enrichment (metabolism pen only), H3 (control-no space restriction), H4 (space restriction with environmental enrichment), and H5 (control-no space restriction). On the eighth day of each housing condition, each animal was exposed to 10 judgement bias trials of each of the three cue types: CS+, CS−, and CS A . We recorded whether animals showed the 'go' or 'no-go' response after each type of cue and collected fecal samples to assess fecal glucocorticoid metabolite concentrations. Peccaries learnt to discriminate CS+ and CS− and maintained this discrimination during the five housing conditions tested. The response to the ambiguous cue (CS A ) varied according to the housing condition. During H1, the peccaries made a similar proportion of 'go' responses to all three types of cue (Ps > 0.07). During H2 and H3, 'go' responses to CSA and CS− cues occurred in similar proportions (Ps > 0.70), but peccaries showed more go responses to CS+ (Ps < 0.03) indicating that they were responding to CSA as if it were more likely to predict the waterjet than food. During H4 and H5, peccaries again made a similar proportion of 'go' responses to all three types of cue, as in H1. During H2 and H3, fecal glucocorticoid metabolite concentrations were higher than during the other tests (208.0 ± 16.4 vs. 141.6 ± 25.9 ngg −1 dry feces, Ps < 0.03). Our results suggest that space restriction may induce physiological stress and influence judgement bias and affective state in peccaries, and that these effects may be offset by environmental enrichment. However, the possibility of a general habituation to the housing conditions across time cannot be ruled out.

Cognitive Bias in Zoo Animals: An Optimistic Outlook for Welfare Assessment

“…The more pessimistic dolphins showed higher levels of anticipatory behavior, in agreement with the reward-sensitivity paradigm where animals in poorer welfare will anticipate their rewards more, since there are fewer of such positive events in their environment [ 57 , 58 ]. These two zoo cognitive bias results highlighted the first potential welfare indicators in dolphins, both of which have direct implications for how the animals are housed and managed [ 59 ]. For example, as a result the dolphins’ caretakers were able to monitor each animal’s anticipatory behavior before training sessions and make an informal judgement about how stimulated it was by its environment and social group at that time, subsequently providing more environmental enrichment if necessary (I. Clegg, personal observation, June 2017).…”

“…When common marmosets ( Callithrix jacchus ) were tested, left-handed animals showed more pessimistic responses in a judgement bias task [ 54 ], while another study found no correlation between bias and rearing conditions [ 50 ]. White-lipped peccaries ( Tayassu pecari ) showed more pessimistic judgements after being net-trapped [ 58 ], and collared peccaries ( Pecari tajacu ) were more pessimistic in response to space restrictions in their environment [ 59 ]. Grizzly bears ( Ursos actos horribilis ) did not show any significant judgement bias differences after accessing various types of enrichment [ 55 ] in an experiment which only used differing levels of positive reinforcement.…”

Comportamento, manejo e bem-estar de mamíferos neotropicais de interesse zootécnico

“…Este paradigma tem sido usado com várias espécies e com objetivos diferentes, como por exemplo, analisar o bem-estar dos animais submetidos ao uso de gaiolas de metabolismo em estudos nutricionais (Oliveira et al, 2016). A restrição de espaço devido ao uso dessas gaiolas pode gerar um estado emocional negativo nos animais e causar empobrecimento no seu bemestar.…”

“…Nesse estudo, teve-se como objetivo testar o uso do paradigma de viés cognitivo/ julgamento acima descrito, para avaliar o efeito da restrição de espaço sob o estado emocional de caititus mantidos em baias de metabolismo em experimentos de nutrição. Seis animais foram submetidos a cinco testes de julgamento: em três dos testes os animais podiam se movimentar livremente, tanto na área de solário quanto nas baias de metabolismo (T1, T3 e T5), enquanto nos outros dois testes houve restrição maior de espaço, com os caititus presos nas baias de metabolismo (T2 e T4) (Oliveira et al, 2016). Em T2 foi adicionado enriquecimento ambiental (EA), 142. mas em T4 não houve a inclusão do EA.…”

“…Adicionalmente, neste estudo, foram monitorados os metabólitos de glicocorticoides excretados nas fezes, para avaliar os níveis de estresse durante os tratamentos. O paradigma do viés cognitivo mostrou-se eficiente para analisar o efeito da redução de espaço sob o estado emocional dos caititus (Oliveira et al, 2016). Durante os três primeiros testes (T1, T2 e T3) os caititus apresentaram proporções similares de respostas 'ir' ao CS +, CS-e CSA, mostrando-se, portanto, sem viés pessimista ou otimista.…”