. -5 â 4 3 2 I 1 """l 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I I f" FEB MAR NOV DEC MAR OCT NOV Fig. 10. Sperm whales in the North Atlantic. Growth curve from conception to weaning. The present study concludes that the sexual cycle of the female sperm whale normally lasts three years. Matsuura (1936) estimated a two-year cycle, but he believed that gestation lasted only one year. Matthews (1938, p. 142) tentatively suggested a cycle of nearly two years; but he
. -5 â 4 3 2 I 1 """l 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I I f" FEB MAR NOV DEC MAR OCT NOV Fig. 10. Sperm whales in the North Atlantic. Growth curve from conception to weaning. The present study concludes that the sexual cycle of the female sperm whale normally lasts three years. Matsuura (1936) estimated a two-year cycle, but he believed that gestation lasted only one year. Matthews (1938, p. 142) tentatively suggested a cycle of nearly two years; but he assumed a lactation period of at least six months by analogy with the condition in whalebone whales, and he considered anoestrum to be absent or of very short duration. There was only one resting whale among the fourteen adult females in Matthews' material, but they were all examined between July and September, that is, during the first half of the southern sexual season, when one would not expect to encounter numbers of resting whales. Growth and age The foregoing study of foetal and calf growth in the sperm whale shows that growth from conception to weaning is not only absolutely but also relatively slower than growth during this period in the great whalebone whales where, for instance, gestation in blue and fin whales lasts a little less than a year and lactation six or seven months, the calves being weaned at about 16 and 12 m. respectively (Mackin- tosh & Wheeler, 1929). The present material offers little information about growth after weaning. For catches between 1949 and 1954 the length frequency curve for the shorter whales (Fig. 2, p. 242) shows no strong peaks which might suggest age groups, nor are the data sufficient for analysis by successive years to see if any features of the length frequencies persist from year to year. Laws (1953) has used periodic
Size: 3577px × 1397px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
