Scientists have found new evidence of an ‘extremely rare’ type of otter in waters north of Lantau – an area where they were previously believed to have been locally extinct since the 1960s.

Conservationists didn’t directly spot the Eurasian Otter – thought to be one of the rarest mammals in Hong Kong – but instead confirmed their presence in the area via genetic tests on a one-dollar-coin-sized pile of dried faeces found on East Brother Island.

In a paper published last month, researchers from the Kadoorie Farm and Botanic Garden said the finding expands the known range of the mammals in the SAR.

The otters have have previously been found in coastal wetlands and rivers mostly in the northwestern part of the New Territories, but now the new data suggests they're also active in offshore islands and the marine environment.

“In this study,” the scientists wrote, “We present the first verifiable evidence of Eurasian Otter in Lantau waters, supporting the possibility that they may inhabit a wider area in Hong Kong and bringing new hope for this locally extremely rare species.”

They say as Eurasian Otters depend on freshwater for drinking and washing, it’s likely they live along the northern coast of Lantau, and only use offshore islets as part of their hunting and nesting grounds.

The researchers added that the importance of marine habitats to local otters has "long been neglected”, and their findings highlight the importance of carefully evaluating the impact of future development projects in North Lantau on the otters.