Individuella skillnader i hägnutnyttjande och solande hos strålsköldpaddor som hålls i grupp

Abstract: The thermal environment is of great importance to all animals, but even more so for ectothermal species that are dependent on external heat provision. Surrounding temperature can be linked to the behaviour and welfare of the animals and the artificial heat and light sources in captivity must be of high quality to enable physiological function, natural behaviour and good health. To be able to evaluate the quality of the enclosure and make improvements, there is a need to understand how the animals use their environment. A group of nine radiated tortoises (Astrochelys radiata) was observed at Parken Zoo during an 11-day period to explore the variation within the group regarding their enclosure usage and basking behaviour. The enclosure was divided into 13 zones based on temperature and light gradients, and the duration of basking was recorded continuously along with instantaneous sampling of the position of the animals every 60 seconds. To account for the size differences of the zones, an electivity index was used. The amount of basking was seen to vary between tortoises and time of day. Smaller individuals did spend more time basking per day and longer time per bout. There were group-level patterns in the way the enclosure was used, but for many of the zones there was a considerable variation between individuals. The largest basking area was over-utilised by most individuals but two used it less than expected by its size. Some zones had a uniform usage while other showed considerable variation between individuals. Because of the different ways the enclosure was used, different tortoises may receive different amounts of UV-B radiation, which is important for their wellbeing. Thermoregulatory needs may explain the differences. However, there are many more aspects that affect the motivation of an individual, such as other enclosure features, conspecifics and the presence or absence of food. The results can be used to make informed decisions at the specific institution regarding enclosure improvements. In a broader context it highlights the importance to consider the behavioural response in addition to the resources provided to the animals when evaluating the welfare and to acknowledge the individual variation within species and within groups.