African savannah elephants ( Loxodonta africana ) released from captivity move differently to wild counterparts

The rewilding of captive animals 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 an evaluation of how released animals are adjusting to their new environments. African savannah elephants once used for tourism are increasingly being rewilded, but such projects rarely consider long-term post-release monitoring, nor do they compare behavioural patterns of released animals with wild ones. In this study, we compared the movement patterns of 12 African elephants with different experiences of captivity: six captive elephants, subjected to a three-year phased soft release in the western Okavango Delta, Botswana, two elephants released over a decade previously and four wild elephants. GPS fixes were used to calculate the 18:00 daily displacement, 30-minute diurnal and nocturnal distances, and home ranges for all study animals. The effects of captivity level, release phase, year and season on these movement metrics were analysed. Movement patterns of captive elephants showed progressive increase in daily displacement and nocturnal distances and associated reduction in diurnal distances, except for home ranges. The home ranges of previously released and wild elephants were 25% larger when resources were abundant (rainy season) than when they were limited (late flood season). The same seasonal patterns were observed on other movement patterns of previously released and wild elephants, but daily displacement and nocturnal movements were larger in wild animals. This variation could be related to sample size or could indicate that rewilded animals may not fully approximate the movement patterns of wild-born individuals. These results highlight the critical importance of long-term monitoring of animals since the movement patterns of released animals may take several years to adjust and converge towards those of wild counterparts.