SINGAPORE - An otter pup may have been lost on Thursday (Jan 26) if not for the spontaneous effort of about 15 otter watchers who staged a late-night rescue.

Four members of the Bishan family of 13 otters were out at the Kallang Basin when two younger ones became separated from their older siblings.

The two-and-a-half-month-old pups were engrossed in the fish they were nibbling on, said Mr N. Sivasothi, a biological sciences lecturer at the National University of Singapore.

"It was an unusual situation where the family was spread out quite far apart," he said.

To the surprise of about five otter watchers observing them, their older siblings left without the young ones.

The two pups finally realised they were alone and tried to follow. One of them was along the water edge and eventually reunited with its family, but the other one wandered off to the middle of the river and disappeared.

The otter watchers were dismayed.

A pup of this age left alone without its family would have been vulnerable to predators like large fish, herons and snakes, traffic or other dangers. It would also not be strong enough to fish on its own, Mr Sivasothi said.

Being young, it could exhaust itself looking for its family, and even drown.

Eventually, otter-watcher Nick Soo located the otter circling in the water, near where it was last spotted. He alerted the other otter watchers in the community.

It is not clear how many are in the group, but there are dedicated otter watchers who keep track of the otter families daily, Mr Sivasothi said.

About 15 people turned up for the rescue, but the pup refused to let them near it.

Many were outside when they got the call, and some went to buy torchlights before they headed down as the sun had set.

It was difficult to get a hold of the agile and slippery otter but they finally caught it, he said.

"Then someone appeared with a laundry basket," Mr Sivasothi said.

With the basket and a blanket, they took the otter back to its holt. It was a long walk, he said, without revealing where the den was.

The otter was returned to its family at about 9.30pm and went to sleep almost immediately. The group last checked on them early on Friday morning and confirmed that the pup was with its parents.

"This is the second unscripted event in which a group of people who watch otters together came together to rescue an otter," said Mr Sivasothi, who said that the group was called upon suddenly but ran the rescue like "a military operation".

"It's nice to see how the otters have brought the kampung spirit back."

In an earlier case last May, six-week-old smooth-coated otter pup named Toby nearly drowned after it fell off a ledge into a canal near Fort Road.

It was finally reunited with its family 10 days later.

The smooth-coated otter, formerly thought to be extinct in Singapore, returned in 1998 as the island's waterways became cleaner.

There are estimated to be about 50 in Singapore now. They are distinct from the Oriental small-clawed otters which can be found in Pulan Ubin.