Release from captivity allows African savannah elephant movement patterns to converge with those of wild and rehabilitated conspecifics

The release of captive animals through rewilding or conservation translocation is an important strategy for the rehabilitation of individuals and ecosystems. Assuming that wild animals are better adapted to their environment than captive ones, comparisons between the behaviour of released animals and their wild counterparts would allow the evaluation of rewilding success. We compared the movement patterns of six captive African savannah elephants, subjected to a three-year soft release in the western Okavango Delta, Botswana, with those of two elephants released over a decade previously and of four wild elephants. GPS fixes at 1800hrs were used to calculate daily displacement, 30-minute diurnal and nocturnal distances, cumulative daily distances, and home ranges for all study animals; the effects of elephant group, phase, year, and season on these movement metrics were analysed. Captive elephants were most affected by the phase and changed their movements after release. After release, the movement patterns of captive elephants were less different from those of rehabilitated elephants than wild elephants, possibly due to sample size, which could indicate that rewilded animals may not be able to fully approximate the behaviour of wild-born individuals. However, the captive elephants should exhibit seasonality in movement patterns just like rehabilitated and wild elephants. These results highlight the critical importance of long-term monitoring of animals to allow the evaluation of release and translocation, which is recommended for other similar studies. The data collection was approved by the UB ethics committee (UBR/RES/IRB/SOC/132).

通过野化放归或保护性易位释放圈养动物，是实现个体康复与生态系统修复的重要策略。基于野生动物较圈养动物更适应生存环境这一前提，对比放归动物与野生同类的行为表现，可用于评估野化放归项目的成效。本研究对6只曾在博茨瓦纳奥卡万戈三角洲西部接受为期3年软放归（soft release）的圈养非洲草原象，与10余年前放归的2头大象及4头野生大象的活动模式开展了对比分析。研究以每日18:00的GPS定位点为基础数据，计算所有研究对象的日移动距离、30分钟间隔的昼间与夜间移动距离、累计日移动距离以及家域范围（home ranges）；同时分析了象群组别、阶段、年份与季节对上述活动指标的影响。分析结果显示，圈养大象的活动模式受阶段因素影响最为显著，且在放归后发生了行为转变。放归后，圈养大象的活动模式与曾放归个体间的差异，小于其与野生大象的差异；这一现象可能受样本量限制，提示野化放归个体或无法完全复刻野生个体的行为模式。不过，圈养大象仍应如同曾放归个体与野生大象一样，表现出活动模式的季节性特征。本研究结果凸显了长期监测放归与易位动物的关键必要性，该结论可供其他同类研究参考借鉴。本研究的数据收集工作已通过博茨瓦纳大学伦理委员会（UB ethics committee，UBR/RES/IRB/SOC/132）的伦理审查。