Understanding the reproductive ecology of humpback whales for their conservation plan in Okinawa Waters

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K16239
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 45040:Ecology and environment-related
• Research Institution: Okinawa Churashima Foundation
• Principal Investigator: Kobayashi Nozomi 一般財団法人沖縄美ら島財団(総合研究センター), 総合研究センター 動物研究室, 主任研究員 (40774401)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: ザトウクジラ / 繁殖生態 / 回帰率 / 出産率 / ソング日周変動 / 衛星発信器 / 沖縄 / 西部北太平洋

Outline of Final Research Achievements

The purpose of this study is to obtain basic knowledge on the breeding ecology of humpback whales which migrate to Okinawan waters for winter breeding season. Using photo identification data which was collected for over 30 years around Okinawan waters, returning rate and breeding rate were calculated, and the analysis on the singing behavior of males was analyzed as well. Furthermore, the utilization of humpback whales in the Okinawan waters during breeding season was also examined using satellite tagging technique. The results showed that Okinawan waters are continuously utilized by the same individuals for a long period of time as a breeding area. The analysis on the within region return index of each individual and the interchange index among other areas in Japan revealed that humpback whales migrating to the Japanese sighting areas including Okinawa are likely to be one group, and that humpback whales also show site fidelity to each areas at some level.

Free Research Field

生態学

Academic Significance and Societal Importance of the Research Achievements

沖縄を含む西部北太平洋系群のザトウクジラは、現在も絶滅危惧種とされており、同集団の保全に向けた知見の拡充や対策が急務とされている。本研究により、沖縄海域が本集団により長期継続的に利用される重要な繁殖海域の１つであることが明らかとなり、また国内複数海域に来遊するザトウクジラが１つの共有の集団である可能性についても明らかとなった。本研究は、世界的に急務とされている西部北太平洋系群の基礎的情報を拡充するとともに、北太平洋全域における本種の保全計画に大きな進歩をもたらす結果となった。