ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



33 



350 

 300 



^ ? 250 



"o. 300 



c 



CD 



Y 250 

 o 



200 



150 



200 



150 



100 



'A 



100 



0 2 



8 10 12 14 16 18 20 22 24 26 28 30 >30 

 Age (years) 



Fig. 19. Standard length of male (upper) and female (lower) Pacific walruses in relation 

 to age. Round symbols are from animals taken at sea (J. W. Brooks, lU. A. Bukhtiarov, 

 J. J. Burns, F. H. Fay, and K. W. Kenyon, unpublished data); triangular symbols are 

 from animals that were reared in captivity (E. D. Asper, G. H. Pournelle, and G. C. 

 Ray, unpublished data). Curves were fitted visually. 



Weight of Body 



Whole body weights of living marine mammals are difficult to obtain in the 

 field, especially for animals as large as walruses. In this and other studies, it has 

 been practical to obtain live weights only of very small infants. Weights of larger 

 animals were obtained from shot specimens, almost always with some unmeas- 

 ured loss of blood. In a few instances, such weights were obtained by cutting the 

 carcass into manageable pieces, weighing each piece, and summing their 

 weights, including those of most of the body fluids. However, in most instances, 

 the whole carcass was weighed by hoisting it aloft with a shipboard crane, to 

 which was affixed a suitable scale. Because of the loss of blood, the weights of 

 most animals older than calves are conservative at best and should be regarded 

 only as approximations of live weight. 



The calves at birth and for most of the first month after birth weigh 45 to 75 kg 

 (Table 4). By the end of their second month, they have increased in weight by 

 only about 30% . If change in weight of captive calves is a valid guide (Fig. 20), 

 the free-living calves probably require about 5 months to double their weight. 

 Their weight at the end of the first year may be about three times the birth 

 weight. 



