ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



113 



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Curvature 



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N = 267 Males 

 N= 44 Females 



40 



20 - 



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El 



N = 372 Males 

 N = 75 Females 



Divergence 



Convergence 



Fig. 76. Comparative curvature and divergence-convergence of tusks of male (open bars) 

 and female (crosshatched bars) Pacific walruses. 



nicely symmetrical, with tips that meet or, less often, cross over (Fig. 77). Those 

 of males of comparable age generally are strongly divergent. 



As noted earlier, the tusks are elliptical in cross section, with the long axis of 

 the ellipse usually at an angle of 25 to 30° from the sagittal plane. In very young 

 walruses, the length of the long axis of the ellipse at the gingival margin is only 

 about two-thirds of that at the proximal (apical) end of the root (Fig. 78). In 

 older walruses, the conical shape of the tusk is increasingly attenuated as the 

 tusks grow rapidly in length but not proportionately in diameter. The point of 

 equality between the gingival and apical diameters is reached in the tusks of 

 females when the clinical crown is about 25 to 30 cm long (at about 10 years of 

 age); in males it is reached when the crown is about 35 to 40 cm long (about 

 15 years of age). Thereafter, with increasing age and decreasing linear growth, 

 the tusks tend to become progressively more spindle-shaped, with maximal cross- 



