Unveiling the process and mechanism of insular dwarfism in large mammals

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04060
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17050:Biogeosciences-related
• Research Institution: Okayama University of Science
• Principal Investigator: Hayashi Shoji 岡山理科大学, 生物地球学部, 講師 (60708139)
• Co-Investigator(Kenkyū-buntansha): 久保 麦野 東京大学, 大学院新領域創成科学研究科, 講師 (10582760)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: シカ類 / 骨組織学 / 生活史 / 島嶼化 / 小型化 / 哺乳類 / 古生物学 / 生態学

Outline of Final Research Achievements

Dwarfism in large mammals on islands is a well-known phenomenon. However, the process involved remains unclear because of the difficulty in comparing animals under controlled factors in natural environment. Here, we examined the life history of cervids isolated for different periods on Japanese islands of various sizes. We detected a transitional change in the life histories of deer from mainland to insular populations; deer on the smaller island exhibited a slower growth rate and a more shrunken body size. Two fossil dwarf deer on an island exhibited even slower body growth and live for a surprisingly long time given their small body size, implying that they may have shifted their life history toward a K-strategy in stable but resource-limited insular environments without predators. These results show how large mammals adapt to island environments by modifying their life histories.

Free Research Field

古生物学

Academic Significance and Societal Importance of the Research Achievements

本研究は日本の様々なシカ類の生態を比較することで、哺乳類の島嶼化の背景にある生態学的なメカニズムとプロセスについての新たな知見を発見することができた（学術的意義）。また、シカ類の生態解明を行った本研究は、増えすぎた現生シカ類が引きおこしている様々な被害（生態系・農作物・人の生活環境）の抑制をするための基礎研究ともなると考えられる（社会的意義）。