In search of the last otters of Hong Kong
Author: Kadoorie Conservation China Department
Three-quarters of the land in Hong Kong is still countryside, and 40% is legally protected! Nonetheless, Hong Kong's countryside faces many threats, and many local species have become very rare, including this top predator, the Eurasian Otter.
Otters were recorded in Hong Kong and Shenzhen as early as the Qing Dynasty. Otters were long hunted for their skins and as pest by fishermen. Also due to water pollution and loss of habitat, otters have vanished from most parts of Hong Kong since the second half of the 20th century. Fortunately, in the 1970s and 1980s, as many rice fields around the Deep Bay area were transformed into fishponds and Mai Po Nature Reserve has been established, the last otters of Hong Kong had found refuge with stable food source.
Since the "rediscovery" of the Eurasian Otter in Mai Po in the late 1980s, otters have been regularly recorded in the reserve. In 2018-2019, a DNA analysis was conducted in Hong Kong for the first time on otter spraint (feces), and it was estimated that as little as 7 otters were living in the Inner Deep Bay (including Mai Po).
In response, KFBG launched the otter survey and conservation project in 2020, the work involved camera trap surveys, field surveys, interview surveys, genetic analysis, awareness raising and capacity building. We have also collaborated with WWF-Hong Kong to conduct long-term monitoring and research on the otters in Mai Po Nature Reserve.
Comprehensive Coastal Search
KFBG has been conducting otter surveys in Hainan, Guangdong, Yunnan and Sichuan provinces since 2012. Based on these experiences, otter surveys has been carried out in Hong Kong since 2020 in areas most likely to have otters. Rocky shores, sandy beaches, mangroves, streams, fishponds, mudflats... So far, camera traps have been set up at over 100 locations, making it the most extensive otter survey ever conducted in Hong Kong.
Getting our hands dirty
Searching and collecting otter spraint is another approach for studying the elusive otters. By analyzing otter DNAs, we can estimate their population size and how far individuals can travel. Genetic materials are better preserved when fresh, so it is our greatest desire to encounter some nice and steaming stools!
We all know that otters like to eat fish, but not all feces with fish scales and fish bones are from otters. Can you guess which of the following pictures are otter’s?
The answers are figure 1, 3 and 5. Figure 3 and 5 are relatively fresh, with a greenish-brown color; figure 1 is relatively old, that is dry and lighter in color. Figures 2, 4, and 6 are pellets, which are undigested food that birds spit out. Among these, Figure 2 and 4 are pellets of kingfishers, and Figure 6 is from cormorant. Compared to otter spraint, bird pellets are more oval or spherical in shape.
As food passes through otters’ gut, some cells on the lining of digestive tracts come off and mix with the feces. Therefore, researchers can identify individual otters by analyzing fecal samples. To know more about our work on DNA analysis of otters, check out our previous blog - Otters’ identity revealed in their stools.
Local Ecological Knowledge
In the past year, we have also conducted large-scale interview surveys (also known as Local Ecological Knowledge surveys) in Hong Kong. Although doing interviews seems less technical, yet this is a widely recognized research method that can provide data that cannot be provided by other means!
Interview surveys can cover a large area fairly quickly, and when locations of otter sightings have been collected, targeted camera trap survey and field surveys can then be conducted. Also, through interviews, other information such as human activities, environmental threats and changes, and otter behaviors etc., can also be collected. Nevertheless, places where no otter sightings do not necessarily mean there were no otters. After all, otters are elusive animals! And we also have to be critical with the interviewees, because people may mistake a Small Asian Mongoose for otter!
Although our work now focuses on field surveys, awareness-raising is also an important aspect of conservation. Early this year, we produced and distributed some wall calendars to the villagers and fishermen near the wetlands in the northern New Territories and other potential habitats of otters and shared with them some facts about otters. Some old people remember otters from their childhood were so excited to talk about them!
The otters will become active again during the cool season. I hope our team great success in finding fresh stools and getting closer in understanding the population status of this rare animal. At last, let’s see some otters through our camera trap lens.