Comprehensive welfare assessment of Eurasian otters (Lutra lutra) in South Korean Zoos using the modified Animal Welfare Assessment Grid (AWAG) and hair cortisol concentration

초록

Animal welfare means meeting animals' physical and psychological needs, minimizing suffering, and supporting their adaptation to the environment. It can be assessed based on an integration of animal-based and resource-based indicators, with additional evaluation of stress levels using physiological measure. Assessing animal welfare helps identify influencing factors, develop strategies for welfare improvement, and detect health issues early. This study aimed to assess the welfare of 17 Eurasian otters (Lutra lutra) housed in eight enclosures across six zoos (five large public zoos and one indoor interactive zoo) in South Korea, identify factors affecting their welfare status, and analyze welfare factors related to chronic stress, ultimately proposing effective improvement strategies. A modified Animal Welfare Assessment Grid (AWAG) was used to evaluate 34 factors across four welfare sections: physical, psychological, environmental, and procedural. Hair cortisol concentrations (HCCs) were measured in 12 Eurasian otters for evaluating chronic stress level. The average welfare scores were as follows: physical (1.65), psychological (3.24), environmental (2.53), and procedural (5.27), with procedural welfare recording the highest score. This was primarily attributed to physical restraint and the high visitor numbers typical of large public zoos. A significant positive correlation between restraint and training (p < 0.01) suggests that positive reinforcement training can help mitigate the negative effects of physical restraint. The indoor interactive enclosure had the highest overall welfare scores, with high psychological scores due to stereotypic behavior and high environmental scores from poor conditions. Abnormal behavior showed positive correlations with environmental factors such as shelter, materials, location suitability, and furnishing/design (p < 0.05). These findings suggest that improving environmental conditions may contribute to reducing stress and enhancing psychological welfare. Another enclosure, which had the second highest overall score, showed particularly high physical and procedural scores. These outcomes were influenced by an individual that died due to disease, highlighting the importance of individualized welfare assessments and regular health monitoring. The average HCC was 18.47 +/- 33.64 pg/mg (median: 8.37 pg/mg, range: 5.31-124.89 pg/mg), with no significant correlation observed with any welfare factors. One individual with a prolonged disease exhibited a relatively high HCC, along with high scores in related physical and procedural factors. While this single case does not allow for generalization, it may suggest a potential association between chronic health conditions and elevated stress levels, warranting further investigation. Future research should include zoos with diverse conditions and refine hair sampling method to better identify welfare factors affecting chronic stress and provide strategies to enhance welfare of Eurasian otters.

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