Age Studies in the Female Humpback Whale, Megaptera nodosa (Bonnaterre), in East Australian Waters

Abstract

Baleen plates, accumulated corpora albicantia, and cores of wax ear plugs are used as age determinants in this study of the female humpback whale. Baleen plates afford a measure of age for whales up to the 3+ age group, but above that age they are of limited use because of wear at the tip of the plate. The mean age at puberty, determined from baleen plates, is between 4 and 5 years. Observations on ear plugs and corpora albicantia from other whales show that this mean age occurs when 9.48 laminations have been laid down in the ear plug. For material collected in June to early September in the three seasons 1952-54 the average number of ovulations per whale was 1.13, but for the material collected in September alone in those seasons, the average number was 1.25. Assuming that two laminations per year are formed in the core of the wax ear plug it has been shown that the rate of accumulation of corpora in the ovaries is 1.10 per year. For several reasons this figure is considered to be too low and an alternative method of calculation indicates that an average rate of aocumulation of 1.48 per year would be closer to the actual rate.