A tale of two otters: settling in Singapore, suffering in China

New research shows a massive decline in China’s otter populations as they recolonise in Singapore, even appearing near the city centre due to the island-nation’s campaign to clean up its rivers.

Few urbanites have seen an otter. Fewer still have seen a “romp” of them. Yet in Singapore, the most urbanized country in the world, commuters can watch whole families breakfast on fish just a few minutes from the city center.

After gaining independence in 1965, Singapore almost immediately began cleaning up its rivers, according to N. Sivasothi, a senior lecturer of biology at the National University of Singapore (NUS). At this point, otters had become extinct on the island.

“The results were [that] the transformation of anoxic black rivers improved to the point [that] fish are well stocked and feeding the smooth-coated otters well,” he said.

It began in 1998, when a pair of smooth-coated otters (Lutrogale perspicillata) sneaked into the Sungei Buloh Wetland Reserve on the north coast from mainland Malaysia. The mangrove-forested reserve sits just across the Johor Strait from Malaysia, and the otters most likely sought refuge there from development projects on the peninsula.

By 2014, Sivasothi had recorded the otter’s expansion across the western and southern coasts of the island. By 2015, a family was dropping pups right in the heart of the city.

Some of these rivers are so polluted that the food sources otters rely on may be killed or suppressed to such low numbers that otters can’t survive.

Bosco Chan, head, Kadoorie Conservation China Department 

Suffering in China

The Singapore story is a sanctuary of hope in a region otherwise largely hostile to aquatic weasels. A paper published in Oryx in 2017 found a devastating drop in otter populations in another part of Asia: China.

China is historically home to three species of otter. Both the smooth-coated otter and the Asian small-clawed otter (Aonyx cinereus) have been recorded in the southern tropical regions of the country, and are classified as Vulnerable on the IUCN Red List. The Eurasian otter (Lutra lutra) — Near Threatened on the IUCN Red List — enjoys the widest distribution in China, inhabiting the country’s larger temperate zone.

The scientists write, however, that “the low number of confirmed records for 2006-2016 suggests that all three otter species are on the verge of extinction in China.” The presence of the smooth-coated otter, in particular, was “unconfirmed” after the five-year study throughout the country — meaning it might be locally extinct.

The study puts the blame for the otter’s decline primarily on commercial hunting. Reports from the commercial fur trade in China indicated both local extinctions and 90 percent declines in regional harvests of Eurasian otters between 1950 and 1985.

“The skin of an otter is regarded by some people as the ‘diamond’ of the fur trade,” says Grace Yoxon of the International Otter Survival Fund (IOSF). Otters, lacking blubber, have incredibly hirsute pelts. Eurasian otter fur can boast up to 50,000 hairs per square centimeter, or about 322,600 hairs per square inch, compared to mink fur’s 24,000 hairs per square centimeter and a human scalp’s 200 hairs per square centimeter.

China officially protected its native otter species in 1989. But Yoxon said she’s “not convinced that fur trapping is abating.”

The scientists expressed hope that, provided there was strict prohibition, otters could rebound quickly from low numbers in China, and even tolerate human-disturbed landscapes as they do in Singapore.

But even if hunting were stopped, otters likely face a new crisis.

Pollution of some rivers might prevent otters from recolonizing vacant habitats that are otherwise suitable, according to Bosco Chan, head of the Kadoorie Conservation China Department at Kadoorie Farm and Botanic Garden in Hong Kong, and a co-author of the 2017 study. “Some of these [rivers] are so polluted [that] the food sources otters rely on may be killed or suppressed to such low numbers [that] otters can’t survive,” he said.

Due to a legacy of industrial pollution, an estimated 28 percent of surface water across rivers in China are “unfit for human contact,” according to a review by non-profit watchdog China Water Risk in 2016. The worst affected river, the Hai, had 41 percent of sections surveyed classified as Grade V+, which in China means not suitable for any use — dead, essentially.

“Otters are top predators and use both land and water habitats,” Yoxon said. “They are […] very susceptible to pollution, and so if you have otters it means that both habitats [land and water] must be in a healthy condition.”

“This is not only important for otters but for all species, including our own,” she added.

Since otters indicate the state of aquatic ecosystems, conservationists often refer to them as a “flagship” species: their preservation ensures the conservation of the biodiversity upon which they survive.

Settling in Singapore

While China proves how easily otters can be wiped out, Chan has reason to be hopeful that they can stage a dramatic comeback.

“Singapore is the best example with the smooth-coated otters living right in the city center,” he said.

Singapore is infamous for its stringent anti-litter laws — even chewing gum is banned. Perhaps less well known is that the country has been cleaning up the environment ever since the late prime minister Lee Kuan Yew’s 1967 plan to turn his country into a clean “garden city beautiful with flowers and trees, and as tidy and litterless as can be.”

Singapore now has the highest density of greenery of any city in the world, based on a 2017 report. One of the recent “garden city” initiatives has been the Public Utility Board’s Active, Beautiful, Clean Waters (ABC Waters) program, which since 2006 has undertaken 32 projects to continue to restore Singapore’s waterways.

ABC Waters recently restored the canalized Kallang River, which runs through Bishan-Ang Mo Kio Park, to a “naturalized” state. In 2014 otters were spotted there; the park is in the middle of Singapore, about 9 kilometers (5.6 miles) upstream from the heavily urbanized Marina Bay estuary.

The so-called Bishan 5 family soon gave birth to five pups, becoming the Bishan 10. Enchanted readers of the country’s leading daily, The Straits Times, voted for the furry, migrant family to represent Singapore on the country’s 51st independence anniversary in 2016.

This story was published with permission from Mongabay.com. Read the full story.

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