Bengal Slow Loris Releases Can Become a Death Trap

Saving a wild animal may seem unquestionably right. Yet what follows a rescue? New scientific research indicates that returning animals to the wild can, at times, result in death rather than freedom.

The research monitored nine Bengal slow lorises after their release in Bangladesh’s Lawachara National Park.

Scientists from Plumploris e.V., Anglia Ruskin University, the University of Western Australia and the Bangladesh Forest Department collaborated on the work.

Using radio collars, the researchers followed every animal for several months. Their findings exposed a major concern.

Bengal slow loris under threat

The Bengal slow loris is Bangladesh’s sole nocturnal primate. This species faces threats from logging, road collisions, hunting and the illegal wildlife trade.

Slow lorises have become highly popular through social media and the pet trade. Online videos of the animals are watched by millions, increasing demand for them.

The International Union for Conservation of Nature (ICUN) classifies Bengal slow lorises as threatened. Wildlife officials regularly seize lorises from traders and people keeping them as pets.

Following rescue, authorities generally return the animals to protected woodland. Although many regard this as a conservation success, the study indicates that the situation is far more complex.

Care for the rescued animals

Before their release, the rescued lorises were kept at the Jankichara Wildlife Rescue Centre within Lawachara National Park.

Staff assessed their health, body weight and injuries. Some arrived underweight or with injuries caused by electrocution or dog attacks.

Based on European zoo husbandry guidance, the animals were given gum, nectar, insects and vegetables.

Every loris was fitted with a lightweight radio collar, weighing under three per cent of its body weight. Researchers observed behaviour at night and logged movements with GPS.

From July 2022 to September 2023, nine lorises were released into the forest.

Most slow lorises died

The results were worrying: just two of the nine lorises lived for more than six months. Three died in the first ten days, while a further four died within months.

Researchers retrieved four carcasses. All had severe bite injuries to the head, face or fingers. The wounds had been inflicted by other slow lorises, a strongly territorial species.

Every animal protects its own territory, and a newcomer entering that space can trigger violent confrontations.

Slow lorises are venomous too. Their sharp teeth can inject venom when they bite, making these attacks potentially fatal.

Slow lorises released into a crowded forest

Lawachara National Park spans roughly 1,250 hectares and includes hills, plantations and remaining areas of old-growth forest.

But the park had also hosted numerous earlier releases. Park records show that 19 slow lorises were released in the Jankichara area during the three years preceding the study.

A high resident loris population may have produced intense competition. All five lorises released close to the rescue centre died. This trend indicates that repeated releases in the same location heightened conflict.

Even where a forest appears extensive, territorial animals require space of their own.

Captivity time matters

The research identified another significant association: lorises that spent more time at the rescue centre survived for fewer days after release.

Some remained in care owing to injuries or political delays. Extended captivity may diminish the abilities needed to survive naturally. Restricted enclosure space may also reduce muscle condition and climbing ability.

Older animals can find it harder to adjust to an unfamiliar environment. Young lorises commonly disperse naturally in the wild, whereas captive animals placed abruptly in unknown territory may become stressed and disorientated.

Moving to survive

The two surviving animals behaved in another way. Darwin, the male, ranged across a notably large area of around 187 hectares.

Nishat, the female, occupied a smaller yet still broad range of roughly 57 hectares. In their initial months, both travelled widely before establishing smaller ranges.

The survivors moved more and rested less. By contrast, the lorises that died spent more time alert and displaying aggressive behaviour. This pattern points to stress and conflict.

By travelling away from densely occupied areas, the survivors avoided lethal encounters.

Habitat was not the main problem

The team also assessed vegetation through satellite data. Survivors and non-survivors both used forest of comparable quality.

This finding demonstrates that lush vegetation alone cannot ensure safety. Most deaths were likely driven by social conflict rather than a shortage of food.

The study underlines a crucial lesson: rescue and release need thorough preparation. Before a release, specialists must assess population density, territory size and animal behaviour. Monitoring over the long term is vital.

Rethinking slow loris conservation

“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,” said study senior author Professor Anna Nekaris.

“Many rescued endangered species are often released because the public expects it, but for animals such as the Bengal slow loris, this is not always the best course of action.”

The drive to produce a feel-good result can sometimes take precedence over rigorous scientific planning.

“Without fully understanding the animal’s behavior, its time spent in captivity and the density of resident populations at the release site, reintroductions may do more harm than good,” noted Professor Nekaris.

Better release planning is needed

“Rescue and release have become an increasingly common practice in Bangladesh. Many wild animals, including slow lorises, are rescued and subsequently released back into the wild,” said study lead author Hassan Al Razi.

This rising practice reflects how strongly people wish to assist wildlife at risk.

“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,” noted Al Razi.

“As a result, certain forests have effectively become dumping grounds for rescued animals and are no longer appropriate release sites.”

“Although our research has focused on the Bengal slow loris and demonstrated the consequences of such practices, we believe similar patterns likely affect many other species.”