246 



DISCOVERY REPORTS 



BODY FORM AND SIZE 



The immature seal of about a year old is very attenuated and almost cylindrical in 

 shape, and with increasing age the principal change is in the development of the 

 thorax and shoulders. This development is considerably more marked in the female 

 than in the male which retains a form reminiscent of the juvenile throughout life, 

 whereas in the large females the thoracic development is very conspicuous indeed. It 

 may be added that the very large head combined with a thin body in youth, or the 

 thoracic development of older animals, greatly facilitates the identification of this species 

 at a distance, since its outline is so different from all the other Antarctic species. 



It was first observed by Bruce, during the voyage of the ' Balaena ', that the female 

 leopard seal is larger than the male, and Barrett-Hamilton (1902) comments on this. 

 Bruce's statement is fully confirmed by the measurements now available. 



The length from the tip of the nose to the tip of the tail is known for eighteen males 

 and ranges from 221 to 305 cm., and of these only one, that is 5-6 per cent, exceeds 

 300 cm. Twenty females range from 221 to 358 cm. and ten of them, 50-0 per cent, 

 exceed 300 cm. At birth the length is about 120 cm. (Matthews, 1929), and growth is 

 evidently very rapid during the first six months; Valette (1906) secured a male and 

 female of small size on 29 December and they were already 189 and 194 cm. respectively, 

 and S.S. 5 of 21 February is 221 cm. During the second half-year of life the rate of 

 growth appears to be less, since the average of four, of both sexes, killed at the age of 

 about a year is only 233 cm. The averages for body and skull length for the four age 

 groups distinguishable are shown below (Table II). The correlation between body and 

 skull length in large animals is not close. For example, the body length of B. 144 is 

 305 cm. and the skull length is 387 mm., whereas B. 145 has a body length of 300 cm. 

 but a skull of 417 mm., and B. 16 with a body of 274 cm. has a skull of 385 mm. 



Table II 



It is appropriate to emphasize here that since the leopard seal is an animal of solitary 

 habit it has to be collected as opportunity offers ; there can be no question of picking 

 the largest specimen, and the series of the two sexes here considered may therefore be 

 properly taken as representative. (For discussion of age grouping see pp. 248, 250-256.) 



Weight. Ross's record of his heaviest specimen, 850 lb., has already been noticed 

 (p. 241). Apart from this the only definite information is that contained in the ' Scotia ' 



