群れはどのようにまとまりを保つのか?~パタスモンキーの集団移動の維持機構~

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2026-01-09 京都大学

サバンナに生息するパタスモンキーを対象に、群れがどのように集団としてのまとまりを維持しながら移動しているのかを、GPS追跡と行動観察を統合して検証した研究である。個体の位置と行動を同時に記録した結果、メスは移動中に見回し行動を行い、周囲にいるコドモの数を把握することで群れの分散を防いでいることが示唆された。一方、オスの見回し行動は、メスとの移動速度差が大きい場面で生じ、その後も差が拡大したことから、群れの同調維持よりも捕食者や他群への警戒に関与する可能性が高いと考えられた。さらに、メスの発する音声が他個体の移動速度を高める効果を持ち、意図的なコミュニケーションとして集団移動を調整していることも明らかになった。本研究は、視覚・聴覚情報に基づく個体行動が集団運動を支える仕組みを示し、野生動物の群集行動理解を大きく前進させる成果である。

群れはどのようにまとまりを保つのか?~パタスモンキーの集団移動の維持機構~
左:食物を探しながら広がって移動するパタスモンキーの群れの様子、中央・右:木に登って見回し行動をするオトナオス(中央)とオトナメス(右)の様子

<関連情報>

視覚と聴覚の手がかりに基づく個々の行動は、パタスモンキー ( Erythrocebus patas ) の集団運動における時空間的調整をどのように促進するのでしょうか? How do individual behaviors based on visual and auditory cues facilitate spatiotemporal coordination in collective movement of patas monkeys (Erythrocebus patas)?

Maho Hanzawa,Yoshiki Morimitsu,Erasmus H. Owusu,Richard D. Suu-Ire & Naofumi Nakagawa
Behavioral Ecology and Sociobiology  Published:08 January 2026
DOI:https://doi.org/10.1007/s00265-025-03684-3

Abstract

Collective movement requires individuals to coordinate their behaviors across time and space. Recent advances in GPS tracking have enabled the recording of whole-group movements and estimation of group cohesion. However, integrating individual behavior with group-level dynamics remains a developing approach. In this study, we combined GPS tracking and behavioral observations to examine visual monitoring and calling related to collective movement in a one-male, multi-female group of wild patas monkeys (Erythrocebus patas), with a focus on sex-specific patterns. Females engaged in visual monitoring when fewer juveniles were nearby, which subsequently lead to having increased proximity of juveniles. This suggests that female visual monitoring play a role in maintaining spatial cohesion with juveniles. In contrast, the single adult male engaged in visual monitoring when the travel speed difference between him and females was large, which subsequently lead to having increased travel speed differences. This implies that the male may be engaging in monitoring primarily as vigilance against predators or conspecific groups, possibly to protect females rather than maintain temporal synchrony with them. Interestingly, female contact calls were associated with increased travel speed of others, particularly under conditions where the caller and others were previously moving at similar speeds. This suggests that calls may serve to accelerate group movement through intentional communication. Overall, our findings suggest that visual monitoring and calling function in context-dependent ways, highlighting the value of integrating movement dynamics, intentional communication and behavioral context to understand the mechanisms of collective coordination in group-living animals.

生物環境工学
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