In the northern part of Okinawajima Island, a large nest box equipped with an automatic camera trap was set up at a height of 5.2 m above the ground from April 2022 to March 2023 to study the reproductive ecology of the Ryukyu long-furred rat Diplothrix legata. This species is endemic to the central Ryukyus and is the largest arboreal murid species in Japan. Videos captured between October and February showed that D. legata was carrying branches and leaves into the nest box and nesting. Calls of newborn rats, sometimes overlapped between different individuals, were recorded from late February to early March, indicating that multiple rats were born in the nest box. These observations suggest that large nest boxes are useful for studying the nesting behavior of D. legata. However, habu snakes Protobothrops flavoviridis were observed entering the nest box and preying on newborns, resulting in no newborns being observed leaving the nests. Although previous studies have recorded the predation of D. legata by habu snakes, this study is the first to provide direct evidence of habu snakes attacking the nesting site and preying on newborns of D. legata.

Published online 20 January, 2025; Print publication 30 April, 2025

ケナガネズミの営巣過程とハブによる新生児の捕食事例．中琉球の固有種で，日本で最も大きな樹上性ネズミ類であるケナガネズミの繁殖生態を調査するために，沖縄島北部において，2022 年 4 月から 2023 年 3 月に自動撮影カメラ付きの大型巣箱を高さ 5.2 m の位置に架設した．10 月から 2 月に，本種が枝や葉を巣箱に運び入れ，営巣する動画が撮影された．その後，2 月下旬から 3 月上旬に複数の新生児の鳴き声が記録された．この結果は，本種が巣箱で複数の新生児を出産したことを示している．本研究により，大型巣箱がケナガネズミの営巣行動調査に有用であることが示唆された．しかし，3 月にハブが巣箱内に侵入し，新生児を捕食した．そのため，巣立ちは確認できなかった．ハブによるケナガネズミの捕食記録はこれまでにもあったが，本研究によってハブが営巣場所を襲撃し，新生児を捕食する直接的な証拠が初めて得られた．