Eurasian Otters in Hong Kong: A Long-Term Study Reveals Their Decline and Resilience

Eurasian otters are elusive and fascinating animals that have been living in Hong Kong for centuries. But their existence in the city is largely unknown and overlooked by most people.

A new research paper has revealed the historical and current status of these otters in Hong Kong, and the challenges they face in the face of rapid urbanization and development.

The paper also highlights the urgent need for conservation actions to protect the last remaining otters and their habitats in Hong Kong.

A long-term study reveals the historical decline of otters in Hong Kong

(Photo : JEFF PACHOUD/AFP via Getty Images)

Researchers have gained new insights into the lives and losses of Eurasian otters in Hong Kong, as detailed in a paper published in the journal Oryx.

The study provides the first long-term overview of the distribution and abundance of the Eurasian otter Lutra lutra in Hong Kong, revealing that the species was much more widespread and common in historical times.

The researchers systematically reviewed and collated all otter records in scientific publications, books, local newspapers, and other popular publications from 1890 to 2020.

A total of 14,231 otter-related newspaper articles were examined.

The study's findings show a drastic reduction in the range and abundance of Eurasian otters in Hong Kong between 1890 and 2020 and indicate that Hong Kong's Deep Bay wetlands have always been the critical habitat for the local otter population.

The decline in otter populations began as early as the 1930s, with the analysis suggesting that this decline was owed primarily to the otter's dependence on lowland wetlands, making it particularly susceptible to urbanization.

Auxiliary infrastructures and water pollution in Hong Kong have exacerbated wetland degradation, to the detriment of otters and their prey.

Among the 70 records analyzed that contained specific locations, 56 (80%) were clustered in the Yuen Long floodplain drained by the Deep Bay catchment.

The records span the 1900s to 2019, suggesting this habitat is critical to the survival of Eurasian otters in Hong Kong.

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The current status and future prospects of otters in Hong Kong

The Eurasian otter has been legally protected in Hong Kong since 1936, making the city a pioneer in otter conservation in Asia.

But, sadly, otters remain the rarest and least known mammal in the region, largely restricted to the Deep Bay wetlands.

The Eurasian otter has the widest distribution of all extant otter species, with a range stretching across Europe, Asia and North Africa, but it is generally considered rare in Asia, and the future of these eastern populations is not secure.

The Hong Kong population was not scientifically studied until the late 2010s.

The result of the first scientific study was shocking: only seven otters could be confirmed by genetic analysis of spraint samples, suggesting that the local otter population may be on the very brink of extinction.

The researchers also found evidence of breeding activity in Mai Po Nature Reserve, which is managed by WWF-Hong Kong.

This reserve is the only site with confirmed breeding otters in Hong Kong. Camera traps captured images of a mother otter with two cubs in 2019.

However, the low-lying region within Hong Kong where most otters can be found has been earmarked for a government-led mega development plan.

This plan involves the reclamation of over 1,700 hectares of land from Deep Bay for housing and infrastructure projects.

The researchers warn that this plan poses a serious threat to the survival of Eurasian otters in Hong Kong, as well as other wildlife that depend on the wetlands.

The researchers urge more conservation actions to protect and restore the habitats of Eurasian otters in Hong Kong.

They also call for more public awareness and education on the importance and plight of this charismatic species.

Bosco Chan, one of the authors of the paper and a conservationist at Kadoorie Farm and Botanic Garden, said: "We hope that our study can shed some light on the forgotten lives of Eurasian otters in Hong Kong and raise public concern for their conservation. Otters are not only an indicator of healthy wetlands, but also a symbol of our natural heritage that we should cherish and protect."