Satellite Remote Sensing Shows Maintenance of Fish Pond Area Improves Persistence of Eurasian Otters in Hong Kong

Urbanization and land cover change are significantly affecting the availability of habitats for wildlife worldwide. However, linking species persistence to large-scale habitat changes is challenging, especially when wildlife monitoring data is lacking. In China, the Eurasian otter ( Lutra lutra ) is a species of conservation concern and is listed as endangered as a consequence of declining populations across the country. Hong Kong is home to a small population of Eurasian otters, which are primarily restricted to a set of wetlands in the inner Deep Bay area. However, the drivers of their historical distribution changes are largely unknown. We combined otter spraint data from 2018 to 2019 with historical records of otter data spanning 1959–2018 to examine otter habitat preference and changes in their distribution, relating this with land cover changes measured by Landsat-5 and Landsat-8 satellite remote sensing in the past (1986 and 1995) and present (2018) using supervised random forest classification. We found that otters showed habitat preference for fish ponds and watercourses, and persisted in areas where fish pond area was more readily available. We also found no significant effect of the extent of land cover changes on otter persistence, suggesting that the species is resilient to some level of fish pond loss and find value in available terrestrial habitats. Our results demonstrate the utility of relating satellite remote sensing data to species distribution data over decadal time scales and highlight the importance of managing terrestrial and wetland habitats for otters and other key species in increasingly urbanized landscapes.