Underdog's perspective: How do poorly armed males fight?

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K06414
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 45040:Ecology and environment-related
• Research Institution: Nara University of Education (2019-2021); Kyoto University (2018)
• Principal Investigator: MURAMATSU Daisuke 奈良教育大学, 自然環境教育センター, 特任准教授 (80635417)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 雄間闘争 / ブラフ / いかさま / 騙し / シグナル / ディスプレイ / ハクセンシオマネキ / Austruca lactea

Outline of Final Research Achievements

Males of the fiddler crab Austruca lactea fight with their major claw, which grows on either the left or right side. Some males have a fragile regenerated claw and are weak in direct fights. To investigate how the males with an inferior weapon fight against other males, naturally occurred male-male contests were observed in a wild population of Austruca lactea. The results show that males with a regenerated claw are less likely to win when they engage in the same-handed contests (right vs. right or left vs. left). Since the claws of two contestants can be grappled tightly in same-handed contests, males with a fragile regenerated claw may retreat soon. These results indicate that males with an inferior weapon recognize the combination of “handedness” of their own and their opponent and behave accordingly.

Free Research Field

動物行動学

Academic Significance and Societal Importance of the Research Achievements

弱者には弱者なりの戦い方がある。本研究では、ハクセンシオマネキという小さなカニの闘争を研究することで、貧弱な武器を持つオスがどのように戦い、武器の弱さが露呈するのを防ぐのか、また武器であるハサミが破壊されるリスクを低減させるのかについて示した。さらに、本種のオスが自分自身と闘争相手の武器が左右いずれにあるのかを認識し、それに応じて行動を変化させることも示した。動物の「利き手」が勝敗に与える影響についてデータで示されるのは珍しく、闘争における左右性の意味を探るうえで重要な発見といえる。