Group fission in the mating season determines the group size

This may help us to understand the mechanism which maintains small group sizes in Yakushima. Male macaques on Yakushima often leave their groups temporarily during the mating season, and so it is difficult for strong coalitions to form between male group members. This provides males from outside the group with opportunities to form intimate relationships with the group’s estrous females. Such intimate relationships between non-group males and group females may lead to the formation of new groups, and this frequent group fission keeps the average group size small.

■References (Books, papers, Web articles, etc.)
ニホンザルの自然社会―エコミュージアムとしての屋久島』 高畑由起夫・山極寿一編 (京都大学学術出版会、2000)
「日本の霊長類——ニホンザル研究の歴史と展望」  山極寿一 (『日本の哺乳類学2.中大型哺乳類・霊長類』所収 pp. 2949.  高槻成紀・山極寿一編 (東京大学出版会、2008))
サルと歩いた屋久島』  山極寿一 (山と渓谷社、2006)


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