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Title :座間味島におけるニホンイタチ(Mustela itatsi)の夏季および秋季の食性と在来種への影響
Title alternative :Food Habits of Introduced Japanese Weasels (Mustela itatsi) and Impacts on Native Species on Zamami Island
Authors :関口, 恵史
小倉, 剛
佐々木, 健志
永山, 泰彦
津波, 滉遵
川島, 由次
Authors alternative :Sekiguchi, Keishi
Ogura, Go
Sasaki, Takeshi
Nagawama, Yasuhiko
Tsuha, Kohjyun
Kawashima, Yoshitugu
Issue Date :30-Dec-2002
Abstract :座間味島に移入されたニホンイタチ(Mustela itatsi)の在来動物に与える影響を把握するために,夏季および秋季の食性調査を糞分析により行った.その結果,検出された餌品目は多岐にわたり,その中で昆虫類は両季節を通じて出現頻度および乾燥重量比とも顕著に高く,座間味島のニホンイタチは昆虫類を主食としていることが特徴的であった.昆虫類以外の主要な餌品目構成には季節的な変化が見られた.夏季には,昆虫類に次いで爬虫類,哺乳類および甲殻類が高い比率を示し,秋季には哺乳類が高い比率を示した.夏季と秋季における比較では,爬虫類のみに有意差が認められ,秋季の爬虫類の乾燥重量は夏季に比べ大幅に減少した.近年,移入種による在来種(特に固有種)への影響は重大な問題となっているが,今回の調査結果から,座間味島のニホンイタチが在来爬虫類に重大な影響を与えていることが示唆された.また,爬虫類の繁殖能力が他の餌品目に比べて低い点を考慮すると,今後,ニホンイタチが爬虫類に及ぼす影響は深刻になると予想される.さらに,座間味島のニホンイタチは島の上位捕食者であると考えられ,その他の在来種の生存を脅かすことに加え,農業被害や人畜共通伝染病の伝播を引き起こす可能性もあり,一刻も早い対策が求められる.
The seasonal diet of Japanese weasel (Mustela itatsi), which had been introduced to the island in 1957 and 1958, was studied by feces analysis during the summer and autumn to evaluate their effect on the endemic species of Zamami Island. Japanese weasels ate a wide variety of prey, consisting mainly of insects. The proportions of prey animals based on their occurrence and dry weights indicated that insects were the most common foods in both seasons. Reptiles and mammals were the next most common prey in summer and autumn, respectively, according to the proportion of dry weight. Considered with the seasonal change of each prey animal, only reptiles showed a significant reduction in proportions of dry weight. There have been many concerns about the influence of introduced animals on endemic species, especially in the case of introduction to a small island. In the present study, it was suggested that the population of endemic reptiles on Zamami Island was particularly susceptible to predation by the Japanese weasel. As well, it is predicted that the Japanese weasel would affect the populations of the other animals since the Japanese weasel is the most dominant predator on this island.
Type Local :雑誌掲載論文
ISSN :0385-437X
Publisher :日本哺乳類学会
URI :http://hdl.handle.net/20.500.12000/1727
Citation :哺乳類科学 = Mammalian science Vol.42 no.2 p.153 -160
Appears in Collections:Peer-reviewed Journal Articles (Faculty of Agriculture)

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