Ecology and conservation of the raccoon dog (Nyctereutes procyonoides) in Japan
Raccoon dogs (Nyctereutes procyonoides viverrinus Temminck) were used as a model species to study wildlife management and conservation issues in the countryside of Japan. Radio-tracking data were used to analyse habitat use, movements, home range configuration and stability, social aspects, and factors influencing raccoon dog behaviour. Comparisons were drawn with European badgers (Meles meles Linnaeus) in the UK in order to highlight aspects of movements and habitat use of omnivorous Carnivores. Two key issues concerning the conservation of raccoon dogs in Japan were investigated: road-kills and agricultural damage. The Japan Highway Public Corporation provided road-kill data on the National Expressways, and a questionnaire survey was conducted on agricultural damage to local governments, authorities of wildlife administration. Socio-cultural issues on wildlife conservation in Japan were critically reviewed and discussed. Two types of habitat users appeared to exist in the study area. One type of raccoon dogs ('mountain type') inhabited a more semi-natural environment, including secondary forest and herbaceous areas, whereas a second type ('village type') inhabited more managed environments, such as rice fields and cropland. The results suggested that habitat selection occurred at home-range and location scales and differed between the two types of raccoon dogs. The mean size of home range of the raccoon dogs was 111 ± 16.9 ha (95% kernel estimate) and 160±34.5ha (95% maximum convex polygon (MCP)). There was no significant difference in home-range size between age classes or sexes. Seasonal home ranges were larger in yearlings than adults, and largest in autumn; and there was no difference between sexes. Season affected nightly movements, i.e. mean inter-fix speed, mean 100% MCP, and mean range span over the night; however, sex and age did not. All variables of nightly movement were smallest in winter. The mean fractal dimension of movements, i.e. degree of 'tortuousity' with self similarity, was 1.226 and significantly differed from 1.0 (a straight line) and 2.0 (a Brownian random movement). The mountain type had significantly larger fractal dimension than the village type, possibly reflecting habitat complexity and/or heterogeneity. Badgers generally preferred pasture and avoided arable habitat, but showed some variability by year and at scales of selection. A Badger Removal Operation may have influenced habitat selection of the badgers. The mean size of home range of badgers was 56.1 ± 7.7 ha (95% kernel estimates) and 56.2 ± 7.3 ha (95% MCP). The mean fractal dimension of the badgers' movements was 1.198 and was significantly different from 1.0 and 2.0. The raccoon dogs and the badgers showed similarities in movements, such as nightly home range, range span over night, and fractal dimension of movements. Sexual differences in spatial use existed in badgers but not in raccoon dogs. Road-kills of raccoon dogs appeared to be the highest, in percentage terms, of all wildlife species in Japan and this figure was linearly related to the traffic. Some road-features, such as whether the road was in a cutting and its proximity to water, were positively associated with road-kills, while the presence of coniferous plantations as roadside habitat was dissociated with road-kills. Nationwide estimates of road-kills of raccoon dogs, based on available data for National Expressways only, were made with different assumptions. Conservative estimates put the number of road-kills at 110,000 - 370,000 per year. The potential for road-kill numbers to be used, after controlling for traffic data, as an index of population trends, is discussed. In a questionnaire survey of agricultural damage sent to 46 prefectures, all respondents (96%) reported some damage by wildlife, and over 80% of respondents reported macaque and boar damage, while nearly 70 % reported raccoon dog and deer damage. Sixty-nine agricultural products were reported to have been damaged by wildlife, and 41 of these by raccoon dogs. Maize and fruits were major crops damaged by raccoon dogs. Although about a half of respondents employed culling, its effectiveness is unclear. Although Japan seems far behind other developing countries in its approach to wildlife conservation issues, the situation could be substantially improved through increased scientific understanding and education. Radical changes may be also required in the legal status of wildlife and its management schemes.