SINGAPORE — Standing on a manhole ­cover in downtown Singapore, dodging double-decker buses and motorcycles, Marjorie Chong sniffs the air and listens for squeaks. "Do you hear that?" she asks.

Chong is searching for otters.

Pollution and deforestation drove away Singapore’s otter population in the 1970s. But as the country cleaned up its waters and reforested land in recent years, otters came back in full force, integrating into urban spaces and learning to navigate one of the world’s most cosmopolitan cities.

Today, to the annoyance of some and the joy of others, the island is home to more than 10 otter romps, or families.

In the Marina Bay area, known for architecturally audacious ­hotels and for one-bedroom apartments that sell for $1.8 million, otters bop in the water and the crunch of fish bones echoes along the boardwalk. Using drainpipes as highways, the carnivorous mammals traverse the city, sometimes popping up in rush-hour traffic, or racing through university campuses.

Otters pushed out of the local rivers and bays by rival families dig homes between buildings. They visit hospital lobbies and condominium pools, hunting for koi fish and drinking from fountains. New families fight for access to food and shelter, in battles that are covered by the local papers and dissected online.

An otter family invaded an apartment complex in Singapore to cool off in the pool on April 6. (Newflare)

As the otter population has boomed, so has otter mania. Otter watchers like Chong spend days tracking the whereabouts of different families, documenting their rivalries, love stories and territorial clashes on social media.

“It’s like ‘Game of Thrones,’ ” said Chong, a retired editor who runs the Ottercity Facebook group. “You realize everyone is just trying to survive.”

On a recent day, Chong scoured canals behind skyscrapers for “Zouk Aunt,” an otter she had been following for years. Zouk Aunt first served as her family’s “nanny,” chaperoning her sister’s pups to swimming lessons and walks, only to be shunned by the group after the two females got into a fight. Now a mother herself, she has to fend for her pups in the financial district, while avoiding the neighborhood’s ruling family, the powerful Bishan otters.

For weeks, Chong and a team of volunteers, who call themselves otter watchers, helped Zouk Aunt and her mate cross a five-lane road into Marina Bay. The volunteers pushed pedestrian crosswalk buttons on traffic lights and waved down cars to prevent the otters from being run over during twice-daily hunting trips.

The otter watchers have quickly become experts, able to identify an animal by a missing toenail or clipped ear. They work with the country’s parks department and zoologists to help abandoned pups return to their families, or get injured animals medical attention.

But not all residents are smitten.

Lynette Foo, 32, was home with her baby when she heard the squeaks. Over a dozen otters wandered past her house and feasted on the 40 koi fish she kept in her backyard pond, some of which her father-in-law had been raising for decades.

“They were eating like they were at a buffet,” she said, adding that the parent otters would blind the fish with their claws first and then let their pups catch them. “They are becoming a nuisance.”

Frustration with the otters mounted during the pandemic, when lockdown restrictions kept people home and gave the animals free rein in the city.

Last year, after a string of otter attacks on koi ponds, one critic wrote a letter to the Straits Times newspaper to call for the animals to be shot with rubber bullets. The demand proved divisive, and even Prime Minister Lee Hsien Loong, who encountered a family of otters frolicking in the yard of the president’s official residence, took a stand. Singaporeans “must find ways to coexist and thrive with our local flora and fauna,” he wrote in a Facebook post.

For otter experts, the critics are missing the point. Higher fencing and sturdier gates are a small price to pay to keep the otters out of areas where they are not welcome.

Singapore’s otters are the envy of researchers around the world, who sometimes work for years without seeing an otter in the wild. They are also testament to Singapore’s reforestation and ­anti-pollution efforts.

When the otters resettled here in 2014, they returned to clean waterways with schools of fish untouched by predators for decades. The city has since implemented an ambitious plan to interweave green and urban ­areas, including creating wildlife corridors so that every resident will live within a 10-minute walk of a park by 2030.

“It doesn’t have to be a concrete jungle,” said Anbarasi Boopal, the co-CEO of Animal Concerns Research and Education Society, Singapore’s wildlife rescue center. “Singapore has a huge potential to be a new model for where greenery, animals and people can learn to live in close proximity.”

Otters are not the only animals that have returned. Wild boars and monkeys have also started appearing in urban spaces. In February, a wild boar jumped out of a bush and attacked a woman, dragging her for a meter before a food delivery driver scared it with a bicycle bell. In June, a family of monkeys was spotted scaling a condominium building.

As animals encroach on metropolitan spaces, and developers dig into forests, Boopal’s organization has created a wildlife management team to respond to altercations between animals and residents and teach people how to handle conflicts.

“There will be resistance. We are so used to having everything presented to us so nicely,” she said. “I tell people, we cannot train the animals. I cannot train the monkey. But I can train you.”