New research has identified the most important factors that determine the success of efforts to relocate large carnivores. The findings could inform global rewilding efforts, from potential Eurasian Lynx reintroductions in the UK to efforts to restore logged tropical forests.
Large carnivores play a vital role in ecosystems across the world, but numbers have crashed over the last few decades. Relocating large carnivores can support their conservation, enabling reintroduction to areas where a species has been exterminated, or to boost the viability of a surviving population. Until now, conservationists have had to make do with little information about what factors determine whether these often expensive efforts are successful or not.
The study was undertaken by an international team led by researchers at the University of Oxford's Department of Biology, Wildlife Conservation Research Unit (WildCRU), and School of Geography and the Environment. The group analysed data from almost 300 animal relocations that took place between 2007 and 2021. These spanned 22 countries in five continents, and involved 18 carnivore species, including bears, hyaenas, big cats, and wild dogs.
Overall, two thirds of relocations were successful, meaning animals survived in the wild for at least six months, the researchers found. They also discovered that success rates have improved significantly since before 2007, from 53% to 70% for wild-born carnivores and doubling to 64% for captive-bred animals.
Iberian Lynx is one of the more challenging large carnivores to relocate, but releasing younger animals and acclimatising them before release can boost success rates (Peter Gasson).
Maned Wolf, Puma and Ocelot all showed a 100% success rate. The lowest success rate was about 50%, with African Lions, Brown Hyenas, Cheetahs, Iberian Lynx and Wolf all presenting more of a challenge.
Another important finding was that a 'soft release', which includes a period acclimatising the animal to the new environment, increased the chances of a successful release by 2.5 times. Releasing younger animals increased the odds too, perhaps because of their greater potential to adapt to a new setting. Additionally, it was shown that captive-born carnivores were 1.5 times less likely to survive in the wild after release than wild-born individuals.
Although the fact that most relocated animals survived is encouraging, the authors say that the low mating success shows the ongoing challenges facing rewilding efforts and, crucially, the importance of protecting habitats that already exist. Overall, only 37% of relocated animals ended up finding a mate or rearing young in their new home range.
Lead author Seth Thomas, from the University of Oxford's Department of Biology, said: "In the last 15 years we have become more successful at translocating and reintroducing large carnivores. This allows us to be optimistic for the future of rebuilding damaged ecosystems around the globe, but we must remember that it is always more important to protect large carnivore populations where they are now before we lose them. Even as we have grown to be more successful, 34% of individual translocations fail and they cannot be seen as a replacement for immediate conservation action to save these populations."
In the near future, relocating large carnivores may become crucial as habitats become altered due to climate change, and if land use changes drive clashes between humans and animals.
In the UK, one of the most nature-deprived countries in the world, there have been calls to reintroduce formerly native apex predators such as Wolf and the Eurasian Lynx.
Professor David Macdonald, from University of Oxford's WildCRU, a co-author for the study, said: "As the UN decade of ecosystem restoration gets underway, the ecological need and political appetite for relocations of large carnivores has never been greater, and they have the potential to contribute more now than ever before to biodiversity conservation. By scrutinising the most geographically comprehensive sample of relocated large carnivores to date, our study makes plain to conservationists and policy makers the urgency of improving rewilding efforts.'
Professor Alastair Driver, the director of the charity Rewilding Britain (who were not directly involved in the research), said: 'This study could not come at a better time here in the UK, with the devolved governments at last consulting positively on the merits of species reintroductions and various groups working hard on the feasibility of reintroducing species such as the European Wildcat and Eurasian Lynx. We still have a long way to go to overcome the misconceptions which dominate societal concerns around sharing our human-dominated landscape with other apex predators, but this report and the successes which it documents, will be hugely valuable in securing a more "grown-up" discussion on the subject. I have no doubt that this will, in turn, lead to well-planned and implemented carnivore reintroductions which only 10 years ago, I would have thought inconceivable in my lifetime.'
Dr Miha Krofel, from the University of Ljubljana and a co-author who worked on lynx reintroductions included in the study, said: "The main reason that allowed us to quantify the higher rate of success is the wider applicability of tracking technology compared to 15 years ago. Nowadays, many practitioners and scientists fit animals with tracking tags for better post-release monitoring of the translocated individuals. This allows us to learn from past releases to improve our interventions in the future."
Thomas, S., et al. "Evaluating the performance of conservation translocations in large carnivores across the world." Biological Conservation (2023). DOI: https://doi.org/10.1016/j.biocon.2023.109909