Examing the adaptive significance of lengthy juvenile periods in genus Tursiops within complex social structures

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K12584
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 90030:Cognitive science-related
• Research Institution: Kindai University
• Principal Investigator: Sakai Mai 近畿大学, 農学部, 講師 (40512299)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: ハクジラ / イルカ / 母子間行動 / 社会行動 / 行動発達 / 鯨類

Outline of Final Research Achievements

In this study, interactions during juvenile periods were described in wild and captive bottlenose dolphins. In wild Indo-Pacific bottlenose dolphins, calves born from primiparous females had a lower survival rate than those born from parous female. Individual differences in swimming distance between mothers and calves and sociosexual behavior between mothers and sons were also demonstrated. Flipper rubbing in which mothers rub calves with its pectoral fins in bottlenose dolphins was found to be a caring behavior to remove old skin from the body surface. In Commerson's dolphins, mothers supported their offspring swimming frequently during the first month of life and decreased thereafter. In orca mother-daughter flipper rubbing, the send-receive bias decreased as the daughters grew older, suggesting that the mother was shifting to a relationship in which she also received some benefit from her daughter.

Free Research Field

動物行動学

Academic Significance and Societal Importance of the Research Achievements

ハクジラ類における子育ては種によっては複数年続き、母子間行動は子の生存率を高める重要な行動である。これまでコドモ期は母から授乳・遊泳サポートなどを受け、社会的学習をする時期という一様な認識であったが、本研究によりコドモの成長とともにこれらの量と質が変化することが明らかになった。ハクジラ類のうち特にハンドウイルカ属は、離合集散で複雑かつ階層的な社会を有する。そのため本研究は、ヒトを含む複雑な社会を有する哺乳類において、コドモ期がいかに重要であるかを知るための比較研究としての意味も大きい。