Wild otters have started breeding in the heart of the city, the first- ever known here to have done so.
Now, experts are worrying about how to best protect them.
Some researchers had considered Singapore's southern coast around Gardens by the Bay too built-up for these threatened native marine mammals that are often found at sea but need a source of fresh water nearby.
But a pair of smooth-coated otters, which first caused a stir in February with their visits to the downtown park, have now raised five pups.
Videos posted on social media over the last month show the family roaming and eating fish along the banks of Marina Reservoir.
They have also been seen inside the Gardens and in its lakes.
The park's deputy director for research Adrian Loo declined to reveal where the otters are suspected to have built their den, in case curious visitors go looking for them.
"If visitors start feeding or playing with them, they might associate humans with food... they might start to harass people," he said, urging visitors to keep their distance when they spot the otters at the Gardens.
There have been signs that humans and otters are getting too close for the staff's comfort.
The animals have been seen scampering after joggers and being chased by children.
"We think they're being fed," said the park's urban ecologist Phira Unadirekkul.
Signs have been put up asking visitors to keep their distance.
National University of Singapore (NUS) otter expert N. Sivasothi was asked to give a talk earlier this year to park staff, who in turn will educate visitors.