放牧下における雄子ヒツジ間の音声によるコミュニケーション Vocal communication of ram lambs on pasture

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本研究は, 放牧下における当歳の雄子ヒツジ問の発声の持続時間と時間間隔, 発声時および後の行動パターンの特徴, 発声対象について, コミュニケーションの基礎的知見を得る目的で行動面からそれらの特徴を検討した。<BR>1) 発声時の行動パターンは, 発声個体ないしは群と発声対象の関係を1つの完了行動として算出して7型に分類した。全体の約4割が餌の要求を目的とした音声と行動であると考えられ, 残り4割は個体への接触ないしは群れへの統合の要求を目的とした音声と行動であると考えられた。残り2割は自己完結の音声と行動であると考えられた。<BR>2) 平均発声総数は, 牧区Iが18.9回/時, 牧区IIは, 25.5回/時であった。1個体あたりの平均発声数に換算すると, 牧区Iでは3.4回, 牧区IIでは3.2回であった。同一個体が2回以上継続して発声したのは24例であり, その平均発声回数は5.2回/頭, 持続時間は0.88±0.34秒 (牧区I), 0.69±0.26秒 (牧区II), 時間間隔は7.44±6.28秒 (牧区1), 6.5±3.89秒 (牧区II) であった。この中には, パターンIの同一個体が連続して20回発声した牧区IIの1例が含まれ, 発声時の行動は移動中であり, これら個体の発声の平均持続時間は0.56秒, 平均時間間隔は5.13秒であり, 他個体と比べ短い傾向にあった。<BR>3) 発声の持続時間の最小値は, 牧区1ではパターンVIの応答個体の0.25秒であり, 牧区IIではパターンIの同一個体が継続して発声した0.2秒であった。また, 最大値は, 牧区1においてパターンIIIの同一個体が継続して発声した1.99秒であり, 牧区IIではパターンVIの応答個体の1.57秒であった。同一個体が継続して発声した場合の持続時間は, 牧区Iでは最大値がパターンIIIの1.37秒, 牧区IIはパターンVの1.24秒であり, 最小値は牧区1が0.3秒, 牧区IIが0.2秒であり, いずれもパターンIであった。牧区間の平均値には有意差はなく, ともに0.5~1秒間に集中していた。牧区Iの発声の持続時間の中央値は, IIと比べて有意に大きく (P<0.01), 0.9秒前後に多くみられた。<BR>4) 発声個体から次の個体が発声するまでの時間間隔は, 牧区Iでは4~10秒間に全体の50%を占め, 牧区IIでは1~5秒間に全体の53%を占めた。牧区1では0.5秒以内に12.1%が応答したのに対して牧区IIでは2.1%であった。0.5秒以内に応答した個体の行動は, 牧区I・IIともに全て佇立時または移動時であった。時間間隔が20秒以上であった個体は, 牧区1では3.3%を占め, パターンIII, IVの佇立時であり, 牧区IIでは7.3%を占め, パターン1の移動時に見られた。同一個体が継続して発声した場合の時間間隔は, 両牧区ともに4~7秒間に集中していた。

The subjects of this study were one year old ram lambs under grazing. The duration and the time intervals of vocalization among them, features of their behavioral patterns and after vocalization and the subjects of vocalization were studied based on their behavior to obtain fundamental knowledge on their communication.<BR>Their behavioral patterns at the time of vocalizations were divided into seven patterns by counting one type of relation between an individual ram lambs or sub-group and the subject of vocalization as one completed behavior. Approx 40% of them seem to be vocalizations and behaviors asking for feed, approx 40% for unity by individual ram lambs or herd, and the remaining 20% being of self-completion.<BR>The average total number of vocalizations was 18.9 times/hour in pasture II and 25.5 times/hour in pasture II. When these figures are converted to a number of average vocalizations per individual ram lamb, 3.4 times/one ram lamb in the pasture I, 3.2 times/one ram lamb in the pasture There were 24 cases where one individual ram lamb vocalized two times or more successively. The average number of vocalizations was 5.2 times/one ram lamb, the duration ranges were of 0.88-10.34 s (the pasture I) and 0.69±0.26 s (the pasture II), the time intervals were 7.44±6.28s (the pasture I) and 6.5±3.89 s (the pasture II). This number includes one case of the pasture II where one individual ram lamb vocalized 20 times in succession. These vocalizations were made while the ram lamb was moving. The average duration of these vocalizations were 0.56 s and the average time interval 5.13 s, both tending to be shorter than those of other individuals.<BR>The minimum duration of vocalization in the pasture I was 0.25 s which was made by an individual of pattern VI when responding to another individual, and that in the pasture II was 0.2 s which was made by the individual of pattern I that vocalized successively. The maximum value in the pasture I was 1.99 s which was made by one individual of pattern III that vocalized successively, and that in the pasture II was 1.57 s which was made by a responding of pattern VI individual. As for the duration of vocalizations made by one individual successively, the maximum value in the pasture I was 1.37 s of pattern III, that in the pasture II was 1.24s of pattern V, and the minimum value in the pasture I was 0.3 s of pattern I, that in the pasture II was 0.2 s of pattern I. There were no significant differences in the average values between the two pastures, the values being concentrated in the range from 0.5 to 1 s. The medians of the vocalization duration in the pasture 1 were significantly larger (P < 0.01), with the values being concentrated around 0.9 s.<BR>As for the time interval from a vocalization of one individual to a vocalization of another individual, 4 to 10 s accounted for 50% of the total in the pasture I and 1 to 5 s accounted for 53% of the total in the pasture II. In the pasture I, 12.1% of individuals responded within 0.5 s, while 2.1% in the pasture II. The behavior of the individuals responded within 0.5 s in both the pasture I and II was either standing or moving. The time interval of 20 s or longer accounted for 3.3% of pattern III or IV in the pasture I and 7.3% of pattern I in the pasture II. The behavior of the responded individuals in the pasture I was standing, while that in the pasture II was moving. The time interval between successive vocalizations made by one individual was concentrated in the range from 4 to 7 s in both the pasture I and II.

収録刊行物

  • 日本緬羊研究会誌 = Japanese journal of sheep science

    日本緬羊研究会誌 = Japanese journal of sheep science 38, 9-18, 2001-12-20

    Japanese Society of Sheep Science

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