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

Abstract

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 4 months of intensive sampling across 2 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.

Analysis of a 131-year longitudinal dataset of the Eurasian otter Lutra lutra in Hong Kong: implications for conservation

“…1). The different localities given in the two editions have caused some confusion among local otter researchers regarding whether otters occurred in the eastern waters of Hong Kong (McMillan et al, 2019, 2022). Although the possibility of otters occurring on these islands cannot be excluded, we think it likely that Ping Chau is a typographical error.…”

“…The otter is a resilient species and can live in human-dominated landscapes provided that healthy riverine and/or coastal ecosystems are available (White et al, 2013; Jo et al, 2020). Urbanization leads to the direct loss of otter habitat, and has been reported to be a major driver of local otter decline (McMillan et al, 2019, 2022). Hong Kong was a modest trading port with a human population of 368,987 in 1901; the population swelled to > 1.6 million in 1941 and reached 3.1 million in 1961 (Census and Statistics Department, 1972; Fig.…”

“…Scientific studies of Hong Kong's terrestrial mammals only began in the 1990s and the status of the Eurasian otter remained obscure, with only occasional reports from the Mai Po Nature Reserve and the surrounding Deep Bay area (Goodyer, 1992; Reels, 1996; Shek, 2003, 2006; Suen, 2003; Shek et al, 2007). The first scientific research on Hong Kong otters was not completed until 2021, in which only seven individuals were genetically identified in a 2-year field study throughout its known local range, with Mai Po Nature Reserve and adjacent wetlands highlighted as the core habitat (McMillan et al, 2022). Despite being considered a species of high conservation priority (Fellowes et al, 2002; Shek, 2003), there is no active conservation programme targeting this population (Agriculture, Fisheries and Conservation Department, 2014a; Kadoorie Farm and Botanic Garden, 2018).…”