Tuesday February 17, 2015
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The Hong Kong status of the Eurasian otter Lutra lutra was referred to as being very rare or extinct by Hill and Phillipps (1981) and possibly extinct by de Silva in 1993 and 1998. There was only one definite observation record dating back to early 1986 (Foster-Turley and Santiapillai, 1990, Foster-Turley, 1991). The record referred to Mai Po, an area comprising mudflats, mangrove forests and some 1,200 ha of traditionally managed fish-ponds situated on the southern banks of Deep Bay (Shenzhen River estuary) in the northwestern New Territories of Hong Kong Special Administrative Region (SAR). The area was designated as a Site of Scientific Interest (SSI) in 1976, but there was no active management for environmental education or conservation until 1984, when WWF Hong Kong began to take over management control. Today WWF Hong Kong jointly manages the area with the Agriculture and Fisheries Department of the Government of Hong Kong SAR. The Mai Po Nature Reserve (MPNR) covers a total of 380 ha (including 110 ha of mangroves), and comprises mainly traditionally managed shrimp ponds, locally called 'gei wais'. For a geographical overview see Irving and Morton (1988). In Hong Kong, all otters are protected under the Wild Animals Protection Ordinance since 1976.
However, Eurasian otters have been sighted and footprints spotted irregularly in MPNR over the last eight years. The reports prompted the authors to check for evident signs on the spot. In early December 1997, while on a short field excursion to MPNR, we could confirm fresh spraints of the Eurasian otter.
Single spraints were found on steel drums supporting a floating boardwalk which guides visitors through the mangrove forest. The size of the area is unlikely to support large numbers of otters and the possibility of genetic exchange with possible otter populations from other areas of Deep Bay remains unclear.
On 14 April 1996, one male Eurasian otter (total length 65 cm, tail length 24 cm) was run over by a car in the reserve. Subsequent gut examination of the otter (by YS) gave evidence of predation on tilapia (Oreochromis mossambicus) due to the presence of pharyngeal plates and scale remains. A few seeds of unknown origin were also found in the stomach. A fresh spraint found and analysed in 1997 also contained remnants of fish hardparts (scales, spines and vertebrae). Tilapia are the most abundant fish in the shrimp-ponds at Mai Po and also present in the fish-ponds around the reserve. In Hong Kong, tilapia are mainly considered as a non-commercial fish. Although we are aware of a lack of systematic otter surveys, we would like to remark that tracks and spraints were more commonly found during the winter months. This may just coincide with the practice of fishermen draining their fish-ponds stocked with mullets, carp and tilapia for harvesting, thereby making prey more available for otters.
No signs of the Asian small-clawed otter Aonyx cinerea, once believed to occur in this area too (Foster-Turley and Santiapillai, 1990), were found.
Together with Inner Deep Bay the wetlands around Mai Po were designated a Ramsar Site in 1995 and are now China's seventh Ramsar Site. However, wetlands and species conservation cannot be achieved by legal designation alone, but are heavily dependent on active support from all levels of the community. Wetlands adjacent to Hong Kong at the neighbouring coast of China suffer from an increase of coastal development projects and water pollution. In Hong Kong, Mai Po (though small in size) still harbours fish- and shrimp-ponds and mangrove forests almost all suitable as otter habitat. MPNR is visited by some 40,000 visitors per year. These not only include local and international birdwatchers, which are attracted due to the area's outstanding importance for migrating birds along the East Asian/Australasian Flyway. Also many members of the public visit the reserve to find out more about it. MPNR's role in wetland conservation and education purposes is furthermore depicted by the fact that 1/4 of the total annual visitors are local students on specially guided visits representing 400 primary and secondary schools. Tours are organized by WWF Hong Kong and sponsored by the Government's Education Department. Thus the authors would hope that this short note will stimulate further interest into assessing the status and habits of an extremely rare mammal species within one of the keystone wetlands in southern China.
de Silva, P.K. (1993). The otter in the wetland ecosystems of South and South-East Asia and the impact of human activities on its survival. In: Copal, B., Hilbricht-Ilkowska, A., Wetzel, R.G. (eds.) Wetlands and ecotones: Studies on land-water interactions. pp. 217-225. National Institute of Ecology, New Dehli.
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