宮崎県青島海岸に集団漂着したカズハゴンドウの生物学的解析 Biological Analysis of a Mass Stranding of Melon-headed Whales (Peponocephala electra) at Aoshima, Japan

We examined 119 melon-headed whales, Peponocephala electra, which stranded on a stretch of about 1.6km of coast at Aoshima (31°47′N, 131°29′E), Miyazaki Prefecture, Japan, in the early morning of 6 January 1982. We confirmed the presence of 84 live animals (70.6% of the total animals examined) during our 4hour examination (10 : 00a.m.-14 : 00p.m.) on 7 January. Body length of 109 animals (68 males and 41 females) examined ranged from 211 to 264cm for males and from 209 to 256.5cm for females. The relationship between body weight (Y in kg) and body length (X in cm) is shown by the following equation : Y=0.0000192X^<2.91>. The sex ratio (female % of the total) of 119 animals was 39.5%. Of 39 females examined on reproductive condition, 34 (87.2% of the total number of females) were sexually mature, comprising 10 pregnant (29.4% of the sexual mature females), 13 lactating (38.2%) and 11 resting animals (32.4%). Sexually mature females ranged from 11.5 to 44.5 years of age and from 231 to 256.5cm in body length. The annual ovulation rate was estimated at 0.28. Possible sexually mature males having a testis weight of 200g or more ranged from 16.5 to 38.5 years of age and from 244 to 264cm in body length. The rate of sexual maturity of 36 males examined was estimated at 72.2%. Maximum testis weight was 1040g. Physically mature animals were found to be 13.5 years or older, and all 14 animals of over 17 years were physically mature. The vertebral formula was C7+T(13-16)+L(15-18)+Ca(39-45)=78-83. Nasitrema gondo was found in the tympanic cavity of all 20 animals dissected in the laboratory.