102 



NORTH AMERICAN FAUNA 74 



Fig. 68. Comparative views of the lower cheek teeth of captive and free-Hving Pacific 

 walruses: upper, from a 7-year-old male reared in captivity at Marineland; lower, from 

 an 11 -year-old male taken in the Bering Sea. (Photos by G. C. Kelley) 



free-living walruses, but they showed little or no sign of abrasion (Fig. 68). 



• Small labial facets, comparable to those in many free-living walruses but 

 lacking the polish and striae, were present wherever the lower teeth contacted 

 the gingiva lateral to the upper tooth row. 



• There were no incisive facets on any of the teeth. 



In most of the captives, the crowns of all of the teeth were somewhat higher 

 than those in free-living walruses and differed also in having significantly greater 

 superficial calcareous deposits (tartar). The near absence of abrasives, whether 

 clam shells or bottom sediments, would account for these differences as well as 

 for the lack of polish and scarcity of incisions. However, in the absence of clam 

 shells and with only small amounts of bottom sediments (in and among the clam 

 meats), these captive animals had developed well-defined occlusal, lingual, and 

 labial facets, closely resembling those in free-living walruses. The presence of 

 these facets indicates that they are not produced exclusively by feeding on hard- 

 shelled moUusks, although they are more clearly expressed in that situation. 

 Conversely, the absence of incisive facets on the teeth of the captives indicates 

 that these facets alone are produced by some items in the natural diet that were 



