New scientific research suggests that returning protected wild animals to their natural habitats is not always successful. In some situations, animals released after long periods of captivity can face serious dangers, turning wild animals into what researchers describe as “death traps.”
The discovery will be published in a magazine Earth ecology and conservation. The research was carried out by primatologist Professor Anna Nekaris OBE from Anglia Ruskin University, along with collaborators from conservation organization Plumprolis eV and the University of Western Australia. Their study investigated the fate of the Bengal slow loris (Nictivus bengalensis) was released in Bangladesh.
Illegal trade in slow lorises and pets
Slow lorises are known for their large eyes and friendly faces, characteristics that unfortunately make them popular in the illegal wildlife trade. Because of this demand, they rank as one of the most trafficked primates in the world.
All slow loris species are listed as endangered, endangered, or endangered by the International Union for Conservation of Nature. Because they are endangered, they are often rescued and then released as part of conservation efforts aimed at rebuilding wild populations.
Tracking Bengal slow lorises after release
Despite these good intentions, new research shows that release programs can sometimes have tragic endings. Scientists fitted nine Bengal slow lorises with radio collars and tracked their movements after releasing them into a national park in northeastern Bangladesh. The park has been used for wildlife stocking before.
The results were grim. Only two of the nine animals returned to the forest and survived. Three died within just 10 days of release, and a further four within six months. Researchers recovered four of the seven bodies, all showing evidence that they had been killed by other slow lorises.
Territorial disputes and poisonous bites
Slow lorises are very territorial animals. They are also the only venomous primates in the world, using specialized teeth to deliver venomous bites. Animals recovered during the study had obvious bite marks on their heads, faces, and fingers, indicating that a dangerous encounter in their territory was the cause of death.
The study also found that animals kept in captivity for longer periods of time tended to survive for fewer days after release. In addition, the released lorises were more mobile and appeared more alert than normal wild Bengal slow lorises.
The two animals that survived traveled a wider range than the one that died. This pattern suggests that survival depended on leaving established territory and avoiding conflict with resident lorises.
Rethinking wildlife rescue and release
Large and charismatic animals, such as big cats, are often subjected to intensive surveillance after being released. In contrast, many small species are not closely tracked, so the outcomes of releases often remain unclear.
Researchers stress that successful wildlife releases require careful planning. It is essential to assess the suitability of the release site and the condition of each animal. Detailed habitat assessments, long-term monitoring, and rehabilitation guidelines tailored to each species increase the likelihood of success.
Lead author Anna Nekaris OBE, professor of ecology, conservation and environment at Anglia Ruskin University in Cambridge, UK, and director of the Little Fireface project, said: ‘Returning confiscated or rescued animals to the wild is “This is always considered a positive conservation story. Our study shows that for highly territorial species like slow lorises, releasing them into areas that are already densely populated can be a death trap.”
“Many protected endangered species are often released due to public expectations, but for animals like the Bengal slow loris, this is not always the best course of action. Without a thorough understanding of the animal’s behavior, time spent in captivity, and population density at the release site, reintroduction can do more harm than good.”
“Rescue and release is becoming increasingly common in Bangladesh. Many wild animals, including slow lorises, are being rescued and subsequently released back into the wild,” said Hassan Alrajhi, team leader and lead author of Purunprolis eV Bangladesh.
“However, in many cases these releases are done inappropriately. For forest-dwelling species, release sites are often selected based on logistical convenience rather than ecological suitability. As a result, certain forests have effectively become dumping grounds for protected animals and are no longer suitable release sites.”
“Although our study focused on the Bengal slow loris and demonstrated the effects of such behavior, we believe similar patterns are likely affecting many other species.”
