They leave a path of misery, destruction, and fish carcasses in their wake.
It's hard to say just how many
In 2020, a brazen coterie of otters known as the Zouk family (named for a local nightclub) went on an outing to a local condominium. The group raided the building's koi pond and then splashed in its pool, bringing its koi kills into the pool.
Earlier this year, a group of otters snuck into a local church and killed nearly 100 fish - around half of which were koi - over several days.
And just last week, a group of otters hit a private koi pond in a northeast part of the city-state, setting upon and killing several fish. The 60-ish owner, who gave his name as Anthony, was left devastated. He told local outlet Mothership he'd cared for some of the fish since childhood and that several of his longtime pet koi had grown to nearly two feet in length.
Anthony told the outlet he was "depressed" by the loss of his "beloved" fish, recalling that he would feed the animals by hand every morning and evening.
"I think what a lot of people don't understand is that people keep koi for years and years," Philip Johns, a biologist at Singapore's Yale-NUS College, told Insider. The average lifespan of a koi fish is around 40 years, according to the Singapore National Zoo, but they can live much longer; one Japanese koi lived to be 226 years old.
Plus, Johns added, koi can be expensive. Some rare ornamental koi can run in the hundreds of thousands of dollars - or even millions, depending on the colors and markings the fish. A 2018 auction of Japanese koi saw one fish go for $1.8 million.
Anthony told Mothership he'd spent around $6,000 outfitting his koi pond, but the price tag on an otter feast can go much higher.
Over the course of several days in 2015, a pack of otters decimated around $64,000 in koi belonging to a homeowner on Singapore's resort island of Sentosa, the Straits Times reported. That same year, the otters cleared out a koi pond at the Shangri-la Resort, also on the island. The fish were reportedly worth around $80,000.
Spending that much money on fish may seem ridiculous to many, but Johns likened it to breeding "prized poodles" and having them killed by wild animals.
"I don't think anybody would question that this is a real tragedy," he said.
"I think if anybody lost a pet that they had invested a lot of time and energy into, they'd be really hurt on top of the financial loss," Johns added.
COVID-19 restrictions seem to have emboldened the animals
Otters have always been native to Singapore, but for many years the population was virtually non-existent. Massive development in the 1960s and 70s destroyed the animal's habitat and led to widespread pollution, National Geographic reported.
But after Singapore began cleaning up its murky waterways in the late 70s, otter families slowly returned.
The majority of the otters now living in the city-state are smooth-coated otters, which can weigh up to 22 pounds, though there is also a smaller population of small-clawed otters. Singapore's otter population is still listed as critically endangered, according to the country's national parks system, but Johns said Singapore's otter pods are having more and more pups.
In light of the attacks, some Singaporeans have begun to see the otters as a nuisance. In 2020, after a series of attacks on pet fish, a Straits Times reader wrote in to recommend a culling of the animals.
"Wild boars have never been encouraged to enter urban areas, neither should otters be just because they look cute," wrote Ong Jungkai.
"We'll throw a few alligators into our canals. See whether can help," wrote one Facebook commenter on a post about the animals earlier this year.
Some residents joked that the pods of 14 or 18 otters should be punished for violating the country's COVID-19 safe-distancing rules, which have capped group sizes under two, five, or eight people at various points throughout the past two years.
The otters have likely been emboldened by Singapore's COVID-19 containment measures, which put the country into a near-total lockdown from April to June 2020.
"When we had the strict circuit breaker in 2020, everything was bolder. There was basically nobody in the streets. It was a ghost town," Johns said. "When you'd look out from your balcony and the roads were just empty, and I think at that point, the otters had free reign."
Public opinion remains fairly planted in the otters' corner
Despite their mild reign of terror, most Singaporeans seem to still hold otters in high esteem. In 2016, the otters were voted the country's animal icon to celebrate Singapore's 51st anniversary.
Even victims of the otters - including former actress Jazreel Low, who in 2020 captured otters killing koi at the beauty spa she owns - have rushed to the animals' defense.
"Otters are living beings as well, and I don't feel right saying that they have to die because of this incident," she told the Singaporean outlet Today Online, adding, "we need to find a way to live with them. Killing them is the easiest way, but I don't think it's the right way out. Coexisting with them might be more difficult, but we just need to learn how to do it."
Besides, Jeffrey Teo, the founder of the otter appreciation Facebook group Ottercity, explained to the South China Morning Post, otters actually embody #lifegoals for many Singaporeans.
"They are exactly who we want to be," he said. "They spend time with family. They like to swim, eat good food and do a little sunbathing."