By Bosco Chan & Michael Hui, 16th October 2023
Call us biased but we believe our home, the tiny Chinese Special Administrative Region of Hong Kong, is a nature lover’s paradise. Despite being famous for its urban skyline, this city—the fourth most densely populated in the world—boasts rich biodiversity and amazing wilderness. Seventy per cent of Hong Kong is essentially rural, with 40% of the city officially protected for conservation, and these landscapes are teeming with wildlife that has recovered from past hunting pressure. Pockets of Hon Kong’s subtropical forests are home to Critically Endangered species such as the Chinese pangolin Manis pentadactyla and the Chinese three-striped box turtle Cuora trifasciata, and the Mai Po Inner Deep Bay Ramsar Site is one of the most iconic wetlands along the East Asian–Australasian Flyway for migratory waterbirds. Plus, the region’s small size of just 1,100 km2 means that all these natural treasures are easily reached.
The Mai Po Inner Deep Bay Ramsar Site is a key site for Eurasian otters in addition to the renowned waterbird assemblage. Photo: WWF-Hong Kong.
It is not all rosy, however, as past and current issues continue to present conservation challenges: natural ecosystems have been degraded, lowland habitats are being encroached by human activities and are grossly under-protected, housing and development pressures are ever increasing, and some of the threatened species that call Hong Kong home are declining and have reached alarmingly low numbers.
Lowland rivers are a key habitat for the Eurasian otter, but most Hong Kong rivers have been engineered into concrete flood channels devoid of wildlife (left) and have been plagued by pollution for decades (right). Photos: Kadoorie Farm and Botanic Garden.
The Eurasian otter Lutra lutra 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 most restricted distribution among local mammals and 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. But how and why has the species vanished from our wetlands? To find out more, we launched a study to investigate the otter’s historical status and the major drivers contributing to its precipitous decline.
A mother otter with two cubs, captured by a camera trap in the 380-ha Mai Po Nature Reserve, which is the only site with confirmed breeding otters in Hong Kong. Photo: WWF-Hong Kong & Kadoorie Farm and Botanic Garden.
We set ourselves the ambitious task of reviewing local newspapers, archival documents and grey literature published between 1890 and 2020, ultimately constructing a 131-year dataset for the species. This involved long visits to libraries and countless hours spent wading through historical newspaper databases and searching through volumes of old books, journals and newsletters for the one magic word: ‘otter’—not the most exciting fieldwork an ecologist can hope for!
But those many hours spent trawling the literature were worthwhile as our work yielded new insights into the past of the local otters. Records show that the Mai Po Nature Reserve and surrounding wetlands have always been the otter’s critical habitat in Hong Kong, and the local population has a strong preference for coastal and alluvial lowland wetlands, making it particularly susceptible to urbanization and pollution. The otter was previously widespread and abundant in Hong Kong, but the population began to decline in the 1930s. The reasons for this decline are difficult to pinpoint, but in contrast to some unsubstantiated reports our findings indicate that hunting played only a small role in the persistent shrinking of the local otter population.
Left: Examples of local natural history books containing information on otters. Right: Eurasian otter Lutra lutra. Photos: Bosco Chan (left) and Quartl/Wikimedia Commons (right).
Despite being in such a precarious status for over half a century, there have been no targeted conservation efforts for the otters of Hong Kong, and only a small portion of the species’ known range is legally protected. There is an urgent need to help conserve the local otter population, now more than ever before. The otter’s current range faces the imminent threat of a government-led mega development strategy called the Northern Metropolis, which will drastically modify the area’s rural landscape, to the detriment of not only the Eurasian otter, but a host of other local biodiversity.
Extensive wetland mosaic in the Northern Metropolis against the Shenzhen skyline on the right; this natural landscape is likely to change for the worse in the coming years. Photo: Kadoorie Farm and Botanic Garden.
In addition to our work to understand the historical status and threats to local otters, we are conducting intensive field surveys throughout the Northern Metropolis to update the species’ current status and emerging threats, so that priority conservation actions can be implemented to prevent the extinction of this charismatic wetland mammal in Hong Kong.
Author and partner surveying otters in mangrove forest of Hong Kong. Photo: Kadoorie Farm and Botanic Garden.
The article ‘Analysis of a 131-year longitudinal dataset of the Eurasian otter Lutra lutra in Hong Kong: implications for conservation’ is available open access in Oryx—The International Journal of Conservation.
