THE STOCK OF WHALES AT SOUTH GEORGIA 363 



Some data collected during season 1929-30 on the presence of different ages of white 

 scars can be adduced in support of migratory movements, though the light they throw 

 upon the age problem is at best uncertain. Leaving aside the mode of formation of the 

 pits and scars (Mackintosh and Wheeler, 1929, pp. 373-9) there remains the fact that 

 whales caught off South Georgia are without exception scarred to a greater or less extent, 

 while those caught in northern waters show the earlier stages of open or crescent pits 

 (Olsen, 1913 ; Risting, 1928 ; Mackintosh and Wheeler, 1929). Every northern migration, 

 then, adds a new batch of open pits, and the whales taken during the southern migration 

 show a fresh series of white scars which can often be distinguished from the older scars 

 by their whiteness, the depth of the central depression and by the fact that a new scar 

 sometimes covers an older one in which the pigment has partly returned and the de- 

 pression filled out. Naturally the more series that are superimposed one upon another 

 the more difficult it is to estimate the number. Evidence of this kind is unsatisfactory in 

 character since it depends largely upon observations of an indefinite quality ; but the 

 difficulties of obtaining any sort of evidence regarding age warrant its inclusion. There 

 are listed in Table IV the lengths of individual female Fin whales, immature by 

 examination or less than 20 metres in length (the critical length of sexual maturity) 

 taken during season 1929-30, with the recognized ages of scars present. 



The fact that the scarred condition of all the whales caught at South Georgia is proof 

 of a north to south migration has been pointed out by Harmer (1931, p. 107). The 

 further inference that the whales have migrated back and forth is not really proved since 

 there are no data concerning the possibility of successive ages of scars made during a 

 prolonged sojourn in northern waters. In this list there is confirmation of the first 

 migratory movement in the presence of newly weaned or still lactating calves, which 

 have come from the north as their scars bear witness. 



If the connection between scar ages and migration is allowed the whales with two 

 series of scars should have been twice in northern waters and twice south, i.e. they are 

 the "immatures verging upon sexual maturity". What then of the group with three 

 ages of scars, of which many are still immature? This suggestive point can be carried 

 further by plotting the length frequencies of all the whales and differentiating between 

 the age series of scars. This has been done in Fig. 3, which brings together all the data 

 collected in 1929-30 relative to the ages of scars. Doubtful readings are omitted; but 

 where the recorded ages were "three or more" the whales have been added to the 

 fourth graph (four recognized age series and over). Two hundred and fifty-one female 

 Fin whales are represented out of the catch of two hundred and seventy-two. 



The group of whales with four and more age series of scars has been at least four 

 times in northern waters and four times south if the correlation between scar series and 

 migration is allowed. With one exception all are mature according to expectation. Of 

 the whales that have apparently made three migrations south the majority are mature, 

 but there are sufficient immatures to justify the statement that, on this evidence, by no 

 means all female Fin whales become mature two years from birth. Therefore the group 

 of "immatures verging upon maturity", considered up to now as a single age group, 



