著者
山田 文雄
出版者
The Mammal Society of Japan
雑誌
哺乳類科学 = Mammalian Science (ISSN:0385437X)
巻号頁・発行日
vol.46, no.1, pp.99-102, 2006-06-30
被引用文献数
3
著者
岩本 俊孝 坂田 拓司 中園 敏之 歌岡 宏信 池田 浩一 西下 勇樹 常田 邦彦 土肥 昭夫
出版者
日本哺乳類学会
雑誌
哺乳類科学 = Mammalian Science (ISSN:0385437X)
巻号頁・発行日
vol.40, no.1, pp.1-17, 2000-06-30
被引用文献数
10

The pellet count method proposed by Morishita et al. (1979) has been widely used in Japan to estimate sika deer population density. However, it is limited in that its usage is only for year-based regular pellet samplings. It cannot be used for irregular sampling periods. This study reveals this limitation through experimental findings that pellets do not decay at a constant rate throughout a year. This study also proposes a modified method applicable to any seasonal/regional sampling by taking into consideration seasonally variable decay rates of pellets. In order to estimate month-specific decay rates of pellets from meteorological data, linear regression and fractional equations were established. Then, employing one of the equations, a computer program was written to estimate sika deer density. This modified method is useful for periodic sampling in which pellets are regularly removed after counting, as well as for one-time sampling made in any region and any month. Discrepancies between the results of density estimations from this modified method and those from the conventional one are also discussed.糞粒消失率を年中一定と仮定した糞粒法によるシカの個体群密度推定式は、1年を単位にした調査以外では使えないことが明らかになった。それは、季節的に糞の消失率が大きく異なるからである。この研究では、季節的に異なる消失率をあらかじめ推定することによって、どのような時期や土地で調査をおこなっても、また任意の調査ルーチンを作ってもシカの密度が推定できる計算方法を提唱する。そのために、土地の気象条件により糞粒の消失率を求めるための推定式を考案した。また、その式により得られた各月の連続消失率を使ってシカの密度推定ができるコンピュータプログラムを開発した。本研究の中で明らかになった糞粒の消失率は、従来使われてきた率に比べ数倍高いものであった。今後は、この違いを生んだ原因を探る研究が必要である。
著者
中下 留美子 後藤 光章 泉山 茂之 林 秀剛 楊 宗興
出版者
The Mammal Society of Japan
雑誌
哺乳類科学 = Mammalian Science (ISSN:0385437X)
巻号頁・発行日
vol.47, no.1, pp.19-23, 2007-06-30
被引用文献数
2

An adult male Asiatic black bear (<i>Ursus thibetanus</i>), 105 kg in body weight and 130 cm in total length, was captured at a fish farm in Miyadamura village, Nagano Prefecture, Japan in June 2005, due to its nuisance activity. We analyzed δ<sup>13</sup>C and δ<sup>15</sup>N in the hairs and plasma of the bear and in the muscles of rainbow trouts (<i>Oncorhynchus mykiss</i>) at the farm to discern whether the bear was actually involved in the farm damages. Both δ<sup>13</sup>C and δ<sup>15</sup>N values in the hairs and plasma were similar to those in rainbow trout muscles, confirming that the bear indeed ate a considerable number of the farm's rainbow trouts. The δ<sup>13</sup>C and δ<sup>15</sup>N values of serum were closer to those of the trout muscles than those of the hairs, indicating that the bear depended heavily on trouts in the spring of 2005 in comparison with the previous year. Moreover, stable isotope levels in the tips of the hairs were closer to those of trout muscles than those at the bases of the hairs. This suggests that the bear depended much more heavily on trouts in the previous spring than in the previous fall.<br>