THE AGE OF FEMALE BLUE WHALES 



261 



The oldest surviving whales were of the order of thirty years old, if the foregoing evidence 

 is accepted, and were found to be sexually active. Four whales were thirty years old or 

 over, and two of these were pregnant. There appears to be no diminution in fertility 

 with increasing age so far as the small number of specimens available in the later stages 

 show. These whales show no climacteric. The life line comes down so abruptly to this 

 age that it is quite possible that intensive whaling has substantially shortened the life 

 span, so that even the oldest reproducing whales might live longer if undisturbed. 



POPULATION AND RECRUITMENT 



The constitution of the adult catch is of the greatest interest, since by examination of 

 this data we may be able to glean some information as to the present condition of the 

 whale population and by inference therefrom make some prognosis. 



I have discussed the age distribution of the whales in the material for 1934-5 an< ^ 

 1935—6 with Mr Edser. 



The correlation between corpora lutea numbers and age enables us to use the corpora 

 lutea frequency curves to represent an age distribution of the adult catch. The frequency 

 curves then may be used as an adult census 

 in a very approximate sense, though the 

 fact that the curves agree so well in their 

 contours is strongly suggestive of the suffi- 

 ciency of the sample in each case as a basis 

 for estimating the age distribution of the 

 adults. 



The age distribution of the catch may 

 itself be applied to an estimate of the age 

 distribution of the adult population in 

 Antarctic waters but only on the condition 

 that the whales caught are a genuine 

 sample of the whales in the sea. In other 

 words it is possible to form an estimate 

 of the population provided that all ages 

 of whales are taken impartially by the 



90 i 



85 



18O 



1934 - 5 



2 75 

 -"90 



ut 

 O 

 < 

 or 



80- 



75 



1935 - B 



10 IS 20 25 



NUMBER OF CORPORA LUTEA 



30 



35 



Fig. 12. 



Average length of whales in each class 

 of corpora lutea numbers. 



whalers. Whalers cannot of course guess the age of the whales they are pursuing, and 

 the question must be transferred to considering whether all lengths of adults are taken 

 impartially, since if all lengths are taken all ages must be also. 



The average length of whales found in each class of corpora lutea numbers was shown 

 for the 1932-3 material (Fig. 6). Since the point at issue is an important one it would be 

 as well to supplement this material with figures from the 1934-5 an ^ 1935—6 data 

 (Fig. 12). The average length in the first four groups is low but increasing with age and 

 rises to 85 ft. by the time five corpora lutea have been accumulated, remaining between 

 85 and 90 ft. throughout the whole of the rest of life. 



