Improvement of Nest Box Investigation Techniques for Study of Arboreal Rodents

27 Mar Improvement of Nest Box Investigation Techniques for Study of Arboreal Rodents

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Abstract

環境影響評価や環境教育の場における巣箱調査の効率向上に資するため, 樹上性齧歯類の巣箱利用を東京都, 神奈川県, 山梨県, 石川県および滋賀県の天然針葉樹林, 落葉樹林, スギ造林地および寺社境内の16カ所において延べ2,664個の巣箱を用いて調査した. ニホンモモンガは天然針葉樹林で最高27%の宿泊率を記録し, 落葉樹林では調査地毎の差が大きかった. ヤマネは落葉樹林を好んだが, 利用率は他種より低かった. ヒメネズミは造林地を含め最も普遍的な巣箱利用者であった. 各調査地の8～11月における平均巣箱痕跡率は, ニホンモモンガで5%, ヤマネで2%およびヒメネズミで10%であった. モモンガとヒメネズミは巣材によって生息を確認できるが, ヤマネについては宿泊個体の現認による慎重な調査が望まれる. 各調査地における最初の巣箱利用痕跡は, 概ね設置1年以内に確認可能であり, 利用度の経年変化は見られなかった. 巣箱は夏季に多く利用され, 巣箱サイズは利用率に影響しなかった. 春に巣箱を設置し, 鳥類繁殖期をさけて夏～秋の数カ月間に延べ300個程度の巣箱を点検すれば, 複数年の調査をしないでも調査地の樹上性齧歯類相はおおむね把握できるといえる.

English Abstract

Aiming at improving effectiveness of fau l survey of arboreal rodents by nest boxes, total of 2,664 nest boxes were used at 16 study sites of different vegetations and altitudes in Japan. The highest occupancy ratio (27%) of Pteromys momonga was recorded at a tural coniferous forest. Ratios at deciduous forests varied by study site. Glirulus japonicus was mainly recorded in deciduous forests with low use ratio. Apodemus argenteus occurred ubiquitously even in coniferous plantations. Average sign ratios of nest boxes during Aug.-Nov. were 5% in P. momonga, 2% in G. japonicus and 10% in A. argenteus. P. momonga mainly used the bark of Japanese cedar Cryptomeria japonica as as a nest material, G. japonicus preferred moss, and A. argenteus fallen and green leaves. The first signs of nest box use appeared two to several months after box erection, and the box use ratio increased from summer to fall. The size of nest boxes had no influence on use ratio of smaller species. Single year inspection of a total of 300 nest boxes during the period from the end of bird reproduction in early summer till the arrival of the cold season seemed sufficient for fau l survey. Nest box survey seemed appropriate for environmental education in the field.