著者
酒向 貴子 川田 伸一郎 手塚 牧人 上杉 哲郎 明仁
出版者
国立科学博物館
雑誌
Bulletin of the National Museum of Nature and Science. Series A, Zoology (ISSN:18819052)
巻号頁・発行日
vol.34, no.2, pp.63-75, 2008-06

The distribution of latrines of the raccoon dog, Nyctereutes procyonoides, was examined from July 2006 to December 2007 in the Imperial Palace grounds, Tokyo, Japan. The raccoon dog is accustomed to defecate at fixed locations, forming holding latrines; thus the distribution of latrines is a good indicator of their abundance. The results suggest that the latrines are widely scattered in the study site, but are more dense in the Fukiage area, where an old-growth broad-leaved forest is established. The latrine sites are used more frequently from September to December, as the number of fresh feces increased in the autumnal season. To examine the seasonal food changes of the raccoon dogs, 10 pieces of feces from some latrines were collected every month and analyzed the indigestible contents in the sampled feces. The food items identified consisted of animal, plant and man-made materials, suggesting that the raccoon dogs were highly omnivorous. The animal materials found from the feces included mammals (4% of total feces), birds (37%), reptiles (2%), amphibians (3%), insects (95%), chilopods (56%), isopods (2%) and gastropods (12%). Invertebrates were the most abundand food item throughout the year. Three coleopteran families, the Carabidae, Staphylinidae and Scarabaeidae, accounted for a large proportion of the insects and they showed seasonal fluctuations. These suggest that the raccoon dogs fed on them as major animal food resources in the study site, and perhaps the seasonality is related to the temporal changes of availability of the insects. The majority of plant materials found in the feces was a variety of seeds, suggesting that the raccoon dogs fed on berries and fleshy fruits throughout the year. The occurrence of seeds decreased from March to April, which coincided with a low availability of fruits. The seeds found in feces were categorized into three types : (1) the short-term berry type including Prunus (Cerasus) spp., Moms spp., Rubus hirsutus and Machilus thunbergii, which occurred only a short term after their fruiting periods ; (2) the long-term berry type, including Celtis sinensis, Aphananthe aspera and Swida controversa, which occurred continuously for three or more months after the fruiting periods ; (3) the acorn type, including Castanopsis spp., Quercus spp. and Ginkgo biloba, which occurred in early spring (January to April) when the other fruits are scarce. The seasonal change of the three fruit types implies that the raccoon dogs consume the available fruits in relation to the successive fruiting periods. The proportion of artificial materials found in the feces was considerably lower than in previous studies carried out in the suburbs of Tokyo, suggesting that the raccoon dogs in the study site strongly depend on natural foods. Most of the natural food items were native to Japan since the past Edo period. Thus we conclude that the preservation of biodiversity in the Imperial Palace grounds was essential for the re-colonization by the raccoon dogs of the Tokyo metropolitan area after the 1970s.
著者
山田 文雄 友澤 森彦 中下 留美子 島田 卓哉 川田 伸一郎 菊池 文一 小泉 透
雑誌
霊長類研究 Supplement
巻号頁・発行日
vol.29, 2013 (Released:2014-02-14)

福島第一原発事故(2011年 3月)による放射性物質の生態系での動態や野生動物の影響を把握するため,地表や土壌中を生活空間とし短寿命のアカネズミなど小型哺乳類を対象に,1)原発から30kmの福島県川内村の国有林(高線量地,空間線量は平均 3.6 μSv/hr,2011年 10月測定)と,2)70kmの茨城県北茨城市の国有林(低線量地,空間線量 0.2 μSv/hr,2011年 12月測定)で継続調査を行った.放射性セシウム濃度(半減期約2年の Cs-134と約 30年のCs-137)は,1年目のアカネズミは高線量地(平均 4,415Bq/ kg生重,最大 18,034-最小 920Bq/kg, n=26)で低線量地(平均 1,124 Bq/kg,5,007-17Bq/kg,n=40)より 4倍,2年目は高線量地(平均 5,950Bq/ kg,最大 19,498-最小567Bq/kg, n=10)で低線量地(平均 370 Bq/kg,882-11Bq/kg,n=30)より 16倍高かった.ヒメネズミは高線量地(平均 5,360Bq/ kg,最大 26,218-最小 91Bq/kg, n=20)で低線量地(平均 221 Bq/kg,7,078-71Bq/kg,n=32)より約 24倍高かった.ヒミズは高線量地(平均10,664Bq/ kg,最大 29,061-最小 41Bq/kg, n=4)で低線量地(平均 650 Bq/kg,2,600-137Bq/kg,n=4)より 16倍高かった.高線量地のヤチネズミ(平均27,290Bq/kg,54,892-12,094, n=4)は高くアズマモグラ(1,017Bq/kg, n=1)は低かった.年変化(事故1年目と2年目)ではアカネズミは高線量地で変化は少ないが低線量地で70%減少し,アカネズミとヒメネズミの濃度は両地で類似し,アカネズミ,ヒメネズミ,ヤチネズミ及びヒミズが高濃度蓄積を示した.
著者
川田 伸一郎
出版者
日本動物分類学会
雑誌
タクサ : 日本動物分類学会誌 (ISSN:13422367)
巻号頁・発行日
no.20, pp.41-50, 2006-02-20

The taxonomy of Japanese moles, genus Mogera, has been confused since the early 1990s, because of the poorly defined type locality of M. wogura and morphological variability within the genus. Genetic research in recent decades has clarified the taxonomic problems of Japanese moles. This paper uses Japanese moles to discuss the importance of karyological study in mammal species recognition. Chromosomal rearrangements are considered likely to have an important role in species diversification of Japanese moles, resulting from postmating isolation mechanisms induced by abnormal meiosis in heterozygotic hybrids. It is well known that recombination leads to gametes with an unbalanced complement of chromosomal segments in inversion or reciprocal translocation heterozygotes. In the case of Japanese moles, four species of Japanese moles, M. etigo, M. imaizumii, M. tokudae and M. wogura, each have a distinct karyotype and/or morphological traits, and are thus considered to be full species endemic to Honshu, Shikoku and Kyushu.