134 NORTH AMERICAN FAUNA 74 



Fig. 94. Examples of naturally occurring supernumerary tusks: left, anterolateral view 

 of the head (skin removed) of an adult female Pacific walrus with bilaterally sym- 

 metrical supernumeraries; center, lateral view of the snout (skin and flesh removed) of 

 an adult male Pacific walrus with asymmetrical supernumeraries; and right, oblique 

 view of the tusks of an adult (male?) Atlantic walrus with a large supernumerary behind 

 the apparently normal right tusk. (Photos by F. H. Fay, G. C. Ray, and J. J. Burns) 



most tusks were most intensively abraded; the posterior tusks had been shielded 

 from abrasion (Fig. 94). 



The frequency of occurrence of anomalous tusks (including supernumeraries) 

 in Pacific walruses certainly is less than 0.1%. From 1952 to 1960, the St. 

 Lawrence Islanders took at least 4,000 walruses, only 2 of which had anomalous 

 tusks; 1 of those had been taken selectively as a curio. At Round Island in July 

 1974, I observed more than 3,000 males, only 1 of which had an anomalous tusk. 



Function of Tusks 



Relation to Feeding 



For a long time, the principal function of the tusks of the walrus was thought 

 to be in digging or raking up clams. Allen (1880:135) cited "Anderson" as the first 

 to recognize that walruses eat mollusks and that they obtain them "from the 

 bottom of the sea by digging with their tusks." Apparently Cranz {in Allen 

 1880:137) was among the first to accept that hypothesis. Its frequent repetition 

 in scholarly and other works in the meantime has led to its being widely adopted 



