Bull. Natl. Mus. Nat. Sci., Ser. A, 42(3), pp. 143–161, August 22, 2016 Long-term Trends in Food Habits of the Raccoon Dog, Nyctereutes viverrinus, in the Imperial Palace, Tokyo Akihito1, Takako Sako2, Makito Teduka3 and Shin-ichiro Kawada4* 1The Imperial Residence, 1–1 Chiyoda, Chiyoda-ku, Tokyo 100–0001, Japan 2Imperial Household Agency, 1–1 Chiyoda, Chiyoda-ku, Tokyo 100–8111, Japan 3Field Work Office, 4–29–2 Asahi-cho, Akishima, Tokyo 196–0025, Japan 4 Department of Zoology, National Museum of Nature and Science, 4–1–1 Amakubo, Tsukuba, Ibaraki 305–0005, Japan *E-mail: [email protected] (Received 31 March 2016; accepted 22 June 2016) Abstract The food habits of the raccoon dogs in the Imperial Palace were examined by fecal analysis focused on the long term trend for five years. A total of 95 taxa (including 58 taxa identi- fied as genera or species) of plant seeds were detected from 163 collected feces in 164 weekly sur- veys. Among them, eight taxa were selected as the food resources for the raccoon dogs in the Imperial Palace. The intakes of these taxa showed seasonal succession, i.e. Aphananthe aspera in January, Idesia polycarpa in February, Rubus hirsutus from May to July, Cerasus spp. in May and June, Morus spp. in June, Machilus thunbergii in July and August, Aphananthe aspera from Sep- tember to December until the following January, and also Ficus erecta in September and Celtis sinensis in December. In March and April, plant harvest is rather poor, and therefore raccoon dogs feed on the inside endosperm of Ginkgo biloba and family Fagaceae to supply the insufficient nutrients as observed by broken seed coats from feces. These spring foods were further supple- mented by the animal food resources shown by additional studies from June 2010 to December 2013. These trends in the main food habits were almost consistent during five years, and thus it is considered that the stable food supply enables maintenance of the population of the raccoon dogs in the Imperial Palace. Key words: fecal analysis, food habits, raccoon dog, the Imperial Palace. from the middle of the 1990’s, and later esti- Introduction mated to be settled based on the biological sur- The raccoon dog, Nyctereutes viverrinus, is an veys of Imperial Palace from 1996 to 2000 (Endo endemic species of canid carnivore distributed all et al., 2000). Recent study confirmed the repro- around Japan excepting Hokkaido and Okinawa duction of the raccoon dog and several individu- Prefecture (Ikeda, 1991; Kim et al., 2015). als inhabited this area exclusively owing to hav- Though there are some capture records of this ing their home ranges in the Imperial Palace species in the Tokyo metropolitan area until the (Kawada et al., 2014). 1950’s, its distribution had shrunk beyond in the The raccoon dog tends to defecate at a certain western part of Tokyo in the 1970’s because of location in its home range called a latrine. Sako the progress of urbanization in those decades et al. (2008) examined the food habits of this (Obara, 1982). However, reports of this species species based on fecal analysis with hand sorting in the Tokyo Metropolis have recently increased method of feces collected in the Imperial Palace dramatically. Raccoon dogs in the Imperial Pal- since April, 2006 to December, 2007, and con- ace have been reported by the imperial guards cluded that the raccoon dogs in this area forage 144 Akihito et al. on natural resources available in this area, mainly which the most dominant was Castanopsis nuts and fruits or insects. Moreover, the foraging sieboldii followed by Aphananthe aspera, trends of several fruits as a main food content in Ginkgo biloba, Zelkova serrata and Quercus certain months were related to the fruiting period acuta (Gardens Division, Maintenance and of the respective plant species. However, further Works Department, Imperial Household Agency, study over a longer period is awaited to certify if 2009). The study site was one of the latrines in these results were transient or a stable peculiarity the Fukiage Gardens studied by Sako et al. for the raccoon dogs in the Imperial Palace. (2008) which was denoted “A1” (Fig. 1). The The fecal analysis of the food habits is benefi- flora around A1 represents Machilus thunbergii, cial due to the aspects of less physical effect and Ginkgo biloba, Aphananthe aspera, Idesia poly- relative ease of collecting feces (Koike, 2013). carpa, Eurya japonica and others as the canopy Recent advances on the food habits of carnivores layer, Hydrangea macrophylla, Fatsia japonica, showed that their foraging on some kinds of Aucuba japonica, Ficus erecta and others as the fruits contributes to seed dispersal (Koike and shrub layer, and Hedera rhombea, Rubus hirsu- Masaki, 2008; Koike et al., 2008), and the sea- tus, Sasa veitchii and others as the herbaceous sonal and annual variations of the plant food layer (Gardens Division, Maintenance and Works resources, e.g. in the Asiatic black bear, Ursus Department, Imperial Household Agency, 2009). thibetanus, have been reported based on long In the Fukiage Gardens, it was estimated that term researches (Koike, 2010). Studies on the several raccoon dogs were living and A1 is food habits of the raccoon dog concerning fruit thought to be a location included in the home intake have been done by Miyata et al. (1989) ranges of these individuals (Kawada et al., and Sakamoto and Takatsuki (2015), but long 2014). More detailed environmental notes were term studies have not been applied. described elsewhere (e.g. Sako et al., 2008). We have conducted hand sorting fecal analysis of the raccoon dogs in the Imperial Palace for 2. Study methods five years from 2009 to 2013 for the further From January, 2009 to December, 2013, we understanding of the fluctuations of fruits usage collected the freshest feces of a raccoon dog, for foods. A similar short study has already been considered to have been excreted after the last published elsewhere (Sako et al., 2008). The sampling, at 2 pm every Sunday. If we decided sampling location of feces was restricted to only that a raccoon dog did not excrete any feces one latrine, which was one of the sampling loca- within a week, sampling was not done. The feces tions in the previous research. This study focused were washed with 0.5 mm mesh, and then the on the succession of the food habits and the included plant seeds were identified and counted. usage of the latrine in the long term. The number of seeds was recorded as “1” to “10” pieces or “＞10” pieces if the number was less than 11 or more than 10, respectively. Materials and methods Because of the omnivorous nature of the rac- 1. Study site coon dog, consideration of the food materials The Imperial Palace is a large green space other than plants need to be evaluated, notwith- with a total area of 115 ha located at the center of standing our focus on the fruits eaten by this spe- Chiyoda-ku, Tokyo Metropolis. The west part of cies. Therefore, after having recorded seeds, the Imperial Palace is called the Fukiage Gardens fecal contents were additionally identified and where there is deep forest with evergreen broad quantified according to Sako et al. (2008) from leaf trees and deciduous broad leaf trees (Konta June 2010 to December 2013. An index of each et al., 2000). According to each tree survey in detected food material to discuss the seasonal this area, there were 133 large trees confirmed, of variation of food habits was calculated by fol- Food habits of raccoon dogs in the Imperial Palace 145 Fig. 1. Study site and the latrine “A1” where we collected the freshest feces of a raccoon dog. Bar indicates 400 m. lowing formula: (Table 1) and one feces collected in April 12, Detection ratio (%)＝number of feces 2009 had no seeds. including each material / examined feces×100 These seeds were classified into 95 taxa which included 58 taxa identified down to genera or species (Appendix 1-5); thus the feces of the rac- Results coon dogs contained highly diversified plant 1. Trends in plant seeds from feces materials. Some parts of these seeds detected We collected 164 feces in the 261 weekly sur- were considered to include accidental intake dur- veys from January 2009 to December 2013. The ing the foraging of animal materials, e.g. insects number of collected feces was fewer from March or chilopods. Therefore, seeds which only one to August, and increased from October to appearance in total survey were rejected, and 35 December (Table 1). There was seldom available taxa were selected to represent the main plant sampling from March to August in 2009, 2010 and food resources of the raccoon dogs in the Impe- 2012. We could not collect any feces in March, rial Palace (Table 3). Most of these seeds were April, June and August of 2011 or in the five from fleshy and juicy fruits when they were ripe months from April to August of 2013. Therefore, enough. On the other hand, a large amount of the rates of collected feces were varied between broken seed coats of Ginkgo biloba, family Faga- 44 to 79% during the five years (Table 2). ceae and family Ebenaceae were found per feces Among 164 analyzed feces, we detected plant in several weeks, but we could not count the seeds from 163 feces (99% of collected feces) number of their seeds (see below). 146 Akihito et al. Table 1. Collection data of feces and detected seeds from feces. Month Jan. Feb. Mar. Apr. May Jun.