124 



NORTH AMERICAN FAUNA 74 



Year 



Fig. 85. Estimated mean annual increments of linear growth in tusks of male (upper) and 

 female (lower) Pacific walruses. Values derived graphicalh' from data in Tables 13 and 

 14 (circles) and from means in Tables 15 and 16 (dots). Curves were fitted by the method 

 of least scjuares. Slope constants (m) for each segment are shown at left. 



(personal communication) reported similar findings in rocky areas at St. 

 Lawrence and Round islands. Fracture of tusks takes place also at sea, for I have 

 seen several bulls with newly broken tusks, far out in the ice during the winter. I 

 suspect that these were fractured in the course of agonistic encounters, for the 

 tusks of opponents often strike resoundingly during threat and subsequent 



