Object Permanence in Captive European Bison (Bison bonasus): Statistical Analysis on Variables Influencing Performance.

Abstract

This study aimed to assess if four European Bisons (Bison bonasus) at the Zoo of Barcelona could learn object permanence by replicating Caicoya's study (Caicoya et al., 2021) on cognitive tasks. The previous study was conducted from a perspective of comparative psychology, which evidently has impacted the procedure and focus of this study. The present research consisted of object permanence, memory with a 30-second delay, and olfactory control. The study was conducted under ethical guidelines with voluntary participation, without food or water deprivation. The procedure included habituation, pre-training, and an experimental phase. One bison discontinued the trials, resulting in three bisons completing the trials. Data were analyzed and compared using the percentage of correct responses, one-sample proportions tests and a generalized linear mixed-effects model (GLMM). Within the percentage of correct responses, Esmeralda showed the highest performance in the object permanence task (66.67%), while Espiga and Estrella performed at 41.67%. The results showed that the European bison did not demonstrate learning of object permanence compared to the previous study, with no statistically significant performance from chance in object permanence and memory task. Analysis of the results showed indications of influences by variables such as potential experimenter biases, framework conditions of the study, and environmental stressors leading to stereotypic behaviours. This study highlights the need to address these variables to improve the validity and reliability of similar assessments and the challenges in replicating studies with captive animals. Key words: Object permanence, cognitive tasks, European Bison, captivity, stereotypic behaviour