AGE-DETERMINATION BY MEANS OF THE OVARIAN CORPORA 469 



(indicated by a dotted line) are probably from females which attained puberty earlier than 5 years. 

 If it were possible to allow for this the frequency distribution in Text-fig. 57 would be slightly more 

 symmetrical. 



40 



30 

 i/i 



a. 



UJ 

 % 



o 20 



a 



1 



or. 



< 



in 



IO 



IO 20 30 



OVARY AGE (YRS) 



40 



Text-fig. 56. Comparison of the ages of individual female fin whales estimated from ear-plugs and ovaries. 



-10 



-5 O +5 



RELATIVE AGE IN YEARS 



+IO 



Text-fig. 57. Frequency distribution of ovary ages about the regression line shown in Text-fig. 56. 



This brief comparison with other methods of age-determination supports the conclusions about the 

 rate of ovulation and the accumulation of corpora reached in this paper. Ovarian counts may be 

 used with confidence to estimate the ages of mature female fin whales. 



Ages determined independently by the three most important methods in use for baleen whales 

 (ovarian corpora, baleen plates, and ear-plugs) are in reasonably close agreement, but all three methods 

 have been criticized on the grounds that it has not yet been possible to check any of them against 



