ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 125 



Table 17. Estimated rates of decrement from 



tusks of male Pacific walruses. 





Tusk length (cm) 



Decrements (cm) 



Age 





Sum linear 







(years) 



Total^ 



inprpmpni"<:b 



Total 



i 1.1111 Licll 1 CL\.\^ 



0 



5.1 



5.1 



0.0 



0.0 



1 



11.4 



11.4 



0.0 



0.0 



2 



18.5 



19.1 



0.6 



0.6 



3 



24.5 



25.9 



1.4 



0.8 



4 



29.0 



31.8 



2.8 



1.4 



5 



32.8 



37.1 



4.3 



1.5 



6 



36.2 



41.7 



5.5 



1.2 



7 



39.3 



45.8 



6.5 



1.0 



8 



42.1 



49.4 



7.3 



0.8 



9 



45.0 



52.8 



7.8 



0.5 



10 



47.8 



56.1 



8.3 



0.5 



11 



50.4 



59.2 



8.8 



0.5 



12 



52.9 



62.1 



9.2 



0.4 



13 



55.5 



65.0 



9.5 



0.4 



14 



57.8 



67.7 



9.9 



0.4 



15 



60.0 



70.3 



10.3 



0.4 



16 



62.1 



72.8 



10.7 



0.4 



17 



64.0 



75.1 



11.1 



0.4 



18 



65.9 



77.4 



11.5 



0.4 



19 



67.6 



79.5 



11.9 



0.4 



20 



69.3 



81.6 



12.3 



0.4 



21 



70.8 



83.5 



12.7 



0.4 



22 



72.3 



85.4 



13.1 



0.4 



23 



73.5 



87.0 



13.5 



0.4 



24 



74.6 



88.5 



13.9 



0.4 



25 



75.5 



89.8 



14.3 



0.4 



26 



76.4 



91.0 



14.6 



0.3 



27 



77.2 



92.1 



14.9 



0.3 



28 





yo.l 



15.2 



0.3 



29 



78.5 



94.0 



15.5 



0.3 



30 



78.9 



94.7 



15.8 



0.3 



31 



79.1 



95.2 



16.1 



0.3 



32 



79.2 



95.6 



16.4 



0.3 



33 



79.2 



95.9 



16.7 



0.3 



34 



79.1 



96.1 



17.0 



0.3 



35 



79.0 



96.3 



17.3 



0.3 



'^Total lengths are astimated means from Fig. 83. 

 ^Sum of linear increments from fitted curves in Fig. 85. 



fighting by males (Miller 1975a). Probably that impact is great enough in some 

 instances to cause fracture. 



Of 94 bulls with fractured tusks that I saw on Round Island, 67 (71 % ) had lost 

 all or part of one tusk. Most of those losses involved less than half of the clinical 

 crown. Fracture of both tusks had taken place in 27 (29 %), also mostly involving 

 less than half of the crown and most often affecting both tusks about equally. 



