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Explainer: What are Raffles’ banded langurs, and how will the Cross Island Line affect them?

SINGAPORE — Mention monkeys in Singapore, and most people would immediately think of the long-tailed macaque.

Explainer: What are Raffles’ banded langurs, and how will the Cross Island Line affect them?

Only an estimated 60 or so Raffles' banded langurs are left in the Central Catchment Nature Reserve. Until the 1920s, their habitat included Changi, Tampines, Bukit Timah, Pandan and Tuas, Wildlife Reserves Singapore said.

SINGAPORE — Mention monkeys in Singapore and most people would immediately think of the long-tailed macaque.

Apart from nature enthusiasts, few would probably know of a rare, second species of primate that is native to the island — the Raffles’ banded langur.

With a tiny population of around 60, these shy and elusive creatures which live among trees are now in the spotlight after the Government announced on Wednesday (Dec 4) that the upcoming Cross Island Line will run under the Central Catchment Nature Reserve.

A ground-level worksite pencilled in for the project will mean that a section of greens that is part of the animal’s habitat will be cleared.

Here is what you need to know about the critically endangered monkey, and how some nature lovers believe its existence may be threatened by the decision to directly align the upcoming MRT line rather than have it skirt around the reserve.

DISCOVERED BY SIR STAMFORD RAFFLES

With its body of black fur and white rings around the eyes, the Raffles’ banded langur is roughly twice the size of the brown macaques that are commonly spotted around the periphery of Singapore’s forested areas.

Formerly known as the banded leaf monkey, it earned its name due to its discovery by Sir Stamford Raffles almost 200 years ago.

A write-up about the langurs by the Wildlife Reserves Singapore (WRS) stated that their habitat extended across Changi, Tampines, Bukit Timah, Pandan and Tuas up until the 1920s.

Habitat loss caused by Singapore’s rapid development eventually caused the langurs to be confined to Bukit Timah Nature Reserve and the Central Catchment Nature Reserve.

Primatologist Andie Ang told TODAY that the construction of the Bukit Timah Expressway (BKE) in 1983 had divided the population by cutting through the forest.

The National Parks Board said on its website that the last member of the troop at Bukit Timah was mauled to death by a pack of dogs in 1987.

SINGAPORE’S NATURAL HERITAGE

Dr Ang, who chairs the Raffles' Banded Langur Working Group that was set up under the auspices of the WRS Conservation Fund, said that the langurs are found only in Singapore and two states in southern Malaysia — Johor and Pahang.

She estimates that in total, only 300 of them are left.

Dr Ang said that the estimated 61 langurs in Singapore are showing some signs of inbreeding. Malaysia’s remaining langurs are also dwindling rapidly.

“A lot of the habitats in Malaysia are not protected because they are cleared for oil palm plantations,” Dr Ang said. “So the ones in Malaysia might go (extinct) faster than ours.”

Noting that 2019 is Singapore’s bicentennial year, she described the langurs as Singapore’s “natural heritage” and said that the animal is vulnerable to further development of built-up areas.

“It is very crucial we protect them,” she stressed.

HOW WILL THE CROSS ISLAND LINE AFFECT THE LANGURS?

Since Dr Ang began her research work in 2008, she has observed some positive trends regarding the langurs in Singapore.

The population has stabilised, with white-furred infants spotted among the troop, due to a growing awareness of the primates among Singaporeans.

However, she fears that the construction of the Cross Island Line could be a repeat of what happened to the population when the BKE was constructed.

When fully completed around 2030, the Cross Island Line will be Singapore’s longest underground train line at 50km to 60km long.

While it will be 70m underground, its construction, however, will require above-ground worksites to be built.

A worksite south of the Singapore Island Country Club's golf course, dubbed A1-W1, will eat into the langurs’ habitat by clearing 3ha of forest — which is roughly equivalent to three football fields, Dr Ang said.

“This area provides crucial connectivity for arboreal animals like the langurs,” she said. “They use it to move from the north to the south.”

Placing the worksite within the forest essentially cuts the habitat apart, which is capable of splitting up the already small population.

“They are already showing signs of inbreeding, so it's best if we can try to facilitate some genetic exchange between them by providing that connectivity.”

Dr Ang noted that while the worksites are only temporary, it will take time for the forest to regrow and be mature enough to be used by animals.

This could mean that forest connectivity may not be restored for up to 20 years after the work is completed.

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In a previous interview with TODAY, Dr Ang had said that it takes time for artificial crossing aids such as rope bridges to be used by the animals. Once their habitat is cleared, they may be pushed onto roads, increasing the risk of roadkill.

When asked about the feasibility of relocating the langurs, Dr Ang pointed out that even if one were able to find and tranquilise the elusive primate, the sedative does not take effect immediately. After being darted, they could climb further up the trees.

The resulting fall when the sedative kicks in could either severely injure or kill them.

Dr Ang believes that a good compromise would be to move the worksite into the golf course area, and prevent any clearing of the forest.

The authorities should consider planting more trees to facilitate animal movement as well.

WHAT ELSE MAY BE AFFECTED

Mr Andrew Tay, executive committee member at Cicada Tree Eco-Place, a non-governmental organisation that promotes conservation and natural heritage, said that the rainforest in the Central Catchment Nature Reserve is species-rich.

“The biodiversity that exists there is incredible, with most species only able to survive in a rainforest habitat,” Mr Tay said.

Clockwise from top: A forest soft shell turtle, a horned frog and a forest crab. Photos courtesy of Kelvin Lim

These rainforest-dependent species include a forest crab, the horned frog and the forest softshell turtle.

A Sunda pangolin curled up in its den in the Night Safari. Photo: Wildlife Reserves Singapore

Dr Vilma D’Rozario, a wildlife activist, said that several critically endangered animals besides the langurs live in the vicinity of the proposed A1-W1 worksite, such as the Sunda pangolin.

There is also the Sunda slow loris (a form of primate), the lesser mousedeer and the colugo (a gliding mammal). Numerous insects and spiders, of which some might be new to science, can be found there, too.

Clockwise from top left: A lesser mousedeer, a Sunda slow loris and a colugo. Photos courtesy of Marcus Chua

“Small animals like spiny hill terrapins and several native snakes and frogs also call that patch of forest home,” Dr D’Rozario said. She is a member of a nature group that the authorities have engaged over the last six years in considering the alignment of the MRT line.

“I personally don’t think sufficient comprehensive biodiversity surveys were done by the Land Transport Authority’s consultant to give a true picture of all the animals that could be affected by the forest clearance,” she said.

“I am truly very disturbed that the direct alignment has been chosen for the Cross Island Line.”

Related topics

environment primate langurs Habitat threat animals Cross Island Line Central Catchment Nature Reserve

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