A new study has found that releasing rescued Bengal slow lorises into the wild can lead to deadly territorial conflicts. Researchers tracked nine animals in a Bangladeshi national park and discovered only two survived, with most killed by other lorises. The findings highlight the need for better planning in wildlife reintroduction efforts.
Researchers from Anglia Ruskin University, Plumploris e.V., and the University of Western Australia examined the outcomes for nine Bengal slow lorises (Nycticebus bengalensis) released into a national park in northeastern Bangladesh. These primates, popular in the illegal pet trade due to their large eyes and gentle appearance, are listed by the International Union for Conservation of Nature as Critically Endangered, Endangered, or Vulnerable. The study, published in Global Ecology and Conservation in 2026, used radio collars to monitor the animals' post-release movements.
The results were sobering: only two of the nine lorises survived. Three died within 10 days of release, and four more perished within six months, totaling seven deaths. Four bodies were recovered, each bearing bite wounds on the head, face, and digits—evidence of attacks by resident slow lorises. As the world's only venomous primates, slow lorises use specialized teeth to deliver toxic bites during territorial disputes.
The research noted that lorises held in captivity longer survived fewer days after release. Released individuals moved more extensively and appeared more alert than typical wild counterparts. The two survivors covered larger areas, suggesting they avoided confrontations by leaving established territories.
Professor Anna Nekaris OBE, senior author and head of the Little Fireface Project, emphasized the risks: "It's assumed that returning confiscated or rescued animals to the wild is always a positive conservation story. Our research shows that for highly territorial species like slow lorises, releasing them into areas that are already densely populated can be a death trap."
She added that public expectations often drive releases without full consideration of behavior, captivity duration, or site population density, potentially causing more harm than good.
Lead author Hassan Al-Razi, team leader for Plumploris e.V. in Bangladesh, pointed to broader issues: "Rescue and release have become an increasingly common practice in Bangladesh... However, in many cases, these releases are conducted inappropriately. For forest-dwelling species, release sites are often selected based on logistical convenience rather than ecological suitability."
He noted that some forests have become unsuitable due to repeated releases, and similar problems may affect other species. The researchers advocate for habitat assessments, long-term monitoring, and species-specific rehabilitation to improve success rates, contrasting with the intensive tracking often given to larger animals like big cats.