Banded leaf monkey

The banded leaf monkey’s range has been largely limited to the Nee Soon Swamp area in the Central Catchment Nature Reserve since 1987, when the last survivor in Bukit Timah met an untimely death.

The disappearance of the banded leaf monkey from Bukit Timah is a tale that has gained “folkloric proportions” in the nature community, said Dr Lum of the Nature Society (Singapore).

It is said that the lone elderly female primate came to the ground, and was mauled to death by a dog (some say a pack of dogs) from a nearby village.

Once common, the monkey has been rare in Singapore since the 1930s, and only one troop was left in Bukit Timah by the 1960s.

While the population in Bukit Timah reserve had been in decline before the BKE was built, the construction of the highway ensured that animals lost from the forest would likely not be able to re-colonise it, Dr Lum said.

In recent years, there has been anecdotal evidence that the monkeys are venturing out of Nee Soon Swamp. But they have yet to be seen in MacRitchie Reservoir where the link is located, said Ms Andie Ang, who studied the monkeys from 2008 to 2010 for her master's thesis. She is now a doctoral student at the University of Colorado Boulder in the United States.

As things stand, it may be a few more years before the link can be used by the banded leaf monkey. Being an arboreal species, they thrive in the tree tops, and rarely come to the ground.

The trees in the eco-link will need to grow much taller to form an “overpass” for the monkeys.

Having two populations of monkeys, in the Central Catchment area and in Bukit Timah, will be better than having one, said Dr Amrita Srivathsan, a biologist at the National University of Singapore. “Their chances of survival will increase,” said Dr Amrita, who has conducted genetic research on the monkeys.

But it will not restore the genetic pool of the troop of monkeys that went extinct in Bukit Timah. A study done by Ms Ang and Dr Amrita found that the remaining monkeys have very low genetic variability - a long-term concern that is difficult to address.

Said Ms Ang: “If they use the eco-link, there are potentially more food sources for the monkeys, but you need more monkeys to expand the gene pool.”