Spraints demonstrate small population size and reliance on fishponds for Eurasian otter (Lutra lutra) in Hong Kong

Lack of data on population sizes and resource requirements are major
impediments to the effective conservation of rare species globally. The
conservation of the Eurasian otter (Lutra lutra) in Hong Kong reflects
many of these key challenges for elusive and difficult-to-study mammals.
It is a rare carnivore that has narrowly escaped extirpation, now
surviving within a human-dominated environment. Using sign surveys and
spraint analysis, we recorded only 40 fresh spraints from 246 otter signs
locations, over four months of intensive sampling across two years.
Records were restricted to the Mai Po wetlands, confirming this as the
core area for Hong Kong’s otter population. Molecular analysis and
microsatellite genotyping identified a minimum of seven individuals, two
pairs of which were likely related. The genetic and sign data together
strongly indicate a small population. Fish dominated the otter diet,
highlighting the importance of fishpond habitats as a premium foraging
resource. Given the rapid changes surrounding the Mai Po area (especially
the new Northern Metropolis Development Strategy), maintaining quality and
connected habitats, in addition to sustaining commercial fishponds will be
key to otter recovery and long-term population viability in Hong Kong.