Discovery reports (1929) Discovery reports discoveryreports01257540inst Year: 1929 442 DISCOVERY REPORTS in males, 23 m. in females), and (3) mature (24 m. in males, 26 m. in females). Again the differences between the maxima are about equal to the ordinary differences in length between the sexes. The tendency towards three dominant length groups is also to be seen in the curves for the 1925-6 season, and in the graph showing the February-May 1925 figures combined with those of season 1925-6. Although the numbers of whales on which these curves are based is small it is difficult to believe t
Discovery reports (1929) Discovery reports discoveryreports01257540inst Year: 1929 442 DISCOVERY REPORTS in males, 23 m. in females), and (3) mature (24 m. in males, 26 m. in females). Again the differences between the maxima are about equal to the ordinary differences in length between the sexes. The tendency towards three dominant length groups is also to be seen in the curves for the 1925-6 season, and in the graph showing the February-May 1925 figures combined with those of season 1925-6. Although the numbers of whales on which these curves are based is small it is difficult to believe that the appearance of these length groups is due to chance, and the explanation seems to be as follows. If breeding took place regularly all the year round one would expect the young whales to appear equally at all sizes at any given time, but as breeding takes place mostly at a particular season there will be batches of 29. 28' 27H 26 25' 24' 23- 22' 21- 20- 1: 18+ 17- 10-- 15- 14- 13- 12- 11- lOH 9- 8- W7-I- BS i-6- S5' 2*' a 3' f-o. O' Zl .â -<- SUMMER ; (north) : (SOUTH females: sexual maturity at 23-7 M.' .males: sexual maturity at 22-6 M. _; .SECOND SEASON SOUTH: 21 M. (APPROX.) <J .FIRST SEASON south: 18 M. (APPROX.) J ..WEANING AT IC M. ⢠⺠|<-WINTER;- (north) SUMMER- (south) -winter-V (north) ..birth at 7 M .< gestation -IâIâIâIâIâr I I Iâr MAY 1ST YEAR TâIâ1âIâIâIâr . MAY JUL 2ND YEAR JUN Fig. 154. Blue whales. Estimated mean curve of growth from conception to sexual maturity. young whales differing in length from one another by an amount equal to a year's growth. It is therefore not unreasonable to suppose that the difference between our two immature groups represents a year's growth. The most uniform results seem to be furnished by the male Blue whales. The facts may be stated as follows. In the summer season at South Georgia male Blue whales are most common at 18-19 m., 21 m. and 24 m. If the calf is weaned at 16 m. it might quite
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