. Scientific Frontline: New study identifies key success factors for large carnivore rewilding efforts

Thursday, February 16, 2023

New study identifies key success factors for large carnivore rewilding efforts

A puma known as Anhanguera is released into Serra do Japi, Jundiaí, state of São Paulo, Brazil, as part of the Vida Livre da Mata Ciliar program.
Photo Credit: Associação Mata Ciliar.

New research led by the University of Oxford has identified the top factors that determine whether efforts to relocate large carnivores to different areas are successful or not. The findings, published today in Biology Conservation, could support global rewilding efforts, from lynx reintroductions in the UK to efforts to restore logged tropical forests.

As apex predators, large carnivores play crucial roles in ecosystems, however their numbers have plummeted over recent decades. Relocating large carnivores can support their conservation, for instance to reintroduce a species to an area where it has been exterminated, or to reinforce an existing population to increase its viability. But to date, there has been little information about what factors determine whether these (often costly) efforts are successful or not.

To investigate this, 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 analyzed data from almost 300 animal relocations which took place between 2007 and 2021. These spanned 22 countries in five continents, and involved 18 different carnivore species, including bears, hyaenas, big cats, and wild dogs.

The 2022 release of a collared leopard into the North Ossetia (Central Caucasus), Russia.
Photo Source: Pavel Padalko.

Key findings

  • Overall, two thirds (66%) of the relocations were successful (where the animal survived in the wild for over 6 months).
  • Success rates for large carnivore relocations have increased significantly since before 2007. For wild-born carnivores, success rates increased from 53% pre-2007 to 70%; and for captive-born animals, success rates doubled from 32 % in pre-2007 to 64 %.
  • The species with the highest success rates included maned wolves, pumas, and ocelots which had a 100% success rate. The species with the lowest success rates (around 50%) were African lions, brown hyenas, cheetahs, Iberian lynx, and wolves.
  • Overall, using a ‘soft release’ increased the odds of success by 2.5-fold. This involves acclimatizing the animal to the new environment before it is fully released.
  • Releasing younger animals (particularly 1 -2-year-olds), also increased success rates. This may be because younger animals have greater behavioral plasticity to adapt to new environments, and they are less likely to have developed homing behaviors.
  • For animals born in captivity, the success rate decreased by 1.5-fold, compared with animals born in the wild.
  • However, just over a third (37%) of the relocated animals were observed to find a mate and/or raise a cub in their new habitat.

"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 scrutinizing 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 David Macdonald, WildCRU, Department of Biology, University of Oxford

Goru, an Eurasian Lynx, who was relocated in 2019 as part of the LIFE Lynx project to save the Slovenian South East Alpine population. Since his release, Goru has reproduced at least three times.
 Photo Credit: Aleš Pičulin.

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.

Lead author Seth Thomas (Department of Biology, University of Oxford) remarked: ‘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 increasingly necessary as habitats become altered due to climate change, and if land use changes increase conflict 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 wolves and the Eurasian lynx.

Professor David Macdonald (WildCRU, Department of Biology, University of Oxford), a co-author for the study, said: ‘For more than half a century, conservationists have fought a dedicated rear-guard action to limit the loss of biodiversity – holding the line is no longer a sufficient aim, it is now time to restore nature, including the large and charismatic carnivores that drive so many ecological processes. Relocations are a crucial arrow in the quiver of possibilities, and our study shines a light on how well it is working, and, importantly, how to make it work better’.

Dr Miha Krofel (University of Ljubljana), 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.’

Published in journalBiology Conservation

Source/CreditUniversity of Oxford

Reference Number: con021623_01

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