亜熱帯野草地における与那国馬の放牧行動

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Yonaguni horse which is a breed of the Japanese Native horse is grazed all the year round in the Zoysia tenuifolia Wild dominant grassland in Yonaguni island. The behavioral ecology of the Yonaguni horses under the extensive management is almost unknown. Understanding the grazing behaviour of the Yonaguni horse is important in order to raise them properly. This study was investigated from the viewpoint of grazing behaviour of the Yonaguni horse, especially maintenance behaviour. A mare in 1-year old age (150 kg body weight) and a stallion in 4-year old age (184 kg body weight) was grazed in the subtropical native pasture year-long. Observation of the Yonaguni horse was carried out continuously for 24 hours from six a.m. till six a.m. next day in June 28～30th, and October 26～28th on 2005. The observation mainly investigated grazing behaviour, rest behaviour, moving behaviour, grooming behaviour, eliminative behaviour yawing, snorting and gassing between mare and stallion were investigated. Grazing behaviour of 24 hours of Yonaguni mare and stallion were the longest time, and the value ranged from 830 minutes to 848 minutes. Secondly resting behaviour of mare and stallion were longer, the time was range from 415-490 minutes. Lying on side behaviour time of a stallion was longer than a mare. Grooming behaviour time was range from 50 minutes to 71 minutes. Although grazing behaviour of horses was often observed in early morning, daytime, late afternoon and midnight, it was measured markedly less at two o'clock afternoon. Resting behaviour of horses was well observed under the spesific tree in the grassland. Standing rest behaviour of mare and stallion were observed throughout a day, especially at two o'clock in the daytime. And lying on belly behaviour and lying on side behaviour were intensively observed during hours between nighttime and early morning. Grooming behaviour of mare and stallion were seen throughout a day, and defication behaviour of both horses were ranged from 7 times to 46 times.与那国島に生息する与那国馬は日本在来馬の一種で，その多くが海岸沿いのコウライシバ優占草地で周年放牧されているが，その行動生態についてはあまり知られていない。与那国馬の放牧行動を把握することは適切な放牧管理を行うためにも重要である。そこで本研究では，野草地における与那国馬の放牧行動，特に維持行動に着目して調査した。与那国島と同様な粗放管理で与那国馬の雄1頭（４歳齢・体重184kg)，雌１頭（１歳齢・体重150kg）を亜熱帯野草地に放牧した。調査は，2005年６月28日～30日までの３日間，10月26日から28日までの３日間の計６日間行い，午前６時から翌日の午前６時までの連続24時間行動観察した。調査項目は，摂取行動(食草，飲水，舐塩）・休息行動・移動・身繕い行動・排泄行動，あくび，スノート，おなら等であった。与那国馬の１日の放牧行動において，食草行動は，もっとも長く，雌馬，雄馬ともに，830～848分の範囲であった。次に休息行動で415～490分の範囲であった。雄馬の横臥位休息は雌馬と比べ有意に長い時間であった。身繕い行動は50～71分の範囲であった。食草行動は，早朝・昼・夕方・深夜に多く観察され，14時には著しく少なかった。休息行動は特定の木の下でよく観察された。立位休息は雌雄ともに１日を通して見られたが特に14時に多く見られた。また伏臥位休息と横臥位休息は，夜から早朝にかけて集中して多く見られた。身繕い行動は，雌雄馬ともに１日を通して見られ，排糞は７～46回の範囲であった。

亜熱帯野草地における与那国馬の放牧行動

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