2021 年 3 巻 p. 93-128
This study examined the morphology, growth and life history of dwarf minke whales to identify and confirm any differences from other minke whale species and subspecies. The study was based on biological samples and data obtained from 16 whales (3 males and 13 females) collected through the 1987/88 to 1992/93 austral summer seasons by the Japanese Whale Research Program under Special Permit in the Antarctic (JARPA). The whales were collected between latitudes 58°23′S and 65°04′S in the Antarctic area between 90°E and 180°. Mean body length at physical maturity was estimated to be 7.16 m for females, approximately 1.5 m to 2.0 m smaller than equivalent values of Antarctic minke whales and North Pacific common minke whales. The characteristic feature of a white shoulder/flipper patch was confirmed and some variations in the overall color pattern was found. Skeletal observations confirmed the previously reported characteristic features on the vertex of the skull. In addition, this study found a longer rostrum, deeply curved mandible, and narrower nasal bone in dwarf minke whales in comparison with other minke whales. All pregnant females had conceived in mid-austral winter (middle of June to early August). Females are likely to attain sexual maturation at 6–6.5 m and at around 7–10 years of age. Stomach contents indicated that dwarf minke whales mainly fed on lantern fishes around the Antarctic Convergence in summer. Analyses by ANCOV revealed significant differences in both external body and skull morphology among different species and subspecies. Furthermore, cluster analyses on the skull morphology revealed differentiation between dwarf minke whales and other common minke whales but they are more closely related to North Atlantic common minke whales. These analyses concurred with previous genetic analyses results. The results of this study provided support for the proposed subspecific status of dwarf minke whales.
