ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



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 g 1400 

 » 1200 

 m 1000 



800 

 600 

 400 

 200 

 0 



1800 

 1600 

 1400 

 1200 

 1000 

 -800 

 -600 

 -400 

 200 

 0 



A CD 



0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 >30 

 Age (years) 



Fig. 21. Whole body weight of male (upper) and female (lower) Pacific walruses in relation 

 to age. Round symbols are from animals taken at sea (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 F. H. Fay, and K. W. Kenyon, unpublished data); triangular symbols are from animals 

 that were reared in captivity (E. D. Asper and G. C. Ray, unpublished data). Adjacent 

 letters identify animals taken in winter (W) and females in or near full-term pregnancy 

 (P). Curves were fitted visually. 



adult males tend to be about 45 % heavier than adult females. The weight of the 

 calf at birth is about 8 % of the mean weight of the fully developed adult female 

 and about 5% of that of the adult male. Examples of relative weights of body 

 parts are shown in Table 5. 



Growth of Reproductive Organs 



Baculum 



I obtained the baculum or os penis from 273 males killed at St. Lawrence 

 Island during the months of May and June. These were fleshed and dried in the 

 field and later boiled in a 5 % aqueous solution of sodium bicarbonate to remove 

 the remaining flesh and oil. After a rinse in fresh water, they were air-dried at 

 room temperature for 3 to 6 months before being weighed and measured. 



Sixty-six of the bacula were from calves less than 1 month old. In that age 

 group, length of baculum ranged from 9.2 to 12.8 cm (mean, 10.6 cm), and dry 

 weights were from 2.7 to 8.1 g (mean, 4.7 g). Data from the bacula of older 

 animals, arranged in order according to their age, indicate that growth in length 

 is rapid in the first 10 years and continues at least to the 15th year (Fig. 22). 

 About 50 % of the growth in length takes place by the 5th year and about 90 % by 

 the 13th year. In 43 adults that were 15 years old or older, the length of the os 

 penis ranged from 47.6 to 62.2 cm (mean, 55.9 cm); weights (Fig. 22) were from 



