ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



105 



Fig. 70. Diagrammatic views of the development and internal structure of the walrus' 

 tusks, as seen in longitudinal section: (a) newborn, (b) at 1 year, (c) at 3 years, (d) in 

 adulthood, and (e) in old age. 



the upper lip, it usually is not apparent in the living animal. 



By 2 years of age, the tusks have increased in length to about 14 to 18 cm in 

 females and 16 to 23 cm in males, about one-third to two-fifths of which is 

 clinically erupted. By this age, the tip of the crown extends usually 2 to 4 cm 

 below the edge of the upper lip and is beginning to show signs of discoloration 



