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NORTH AMERICAN FAUNA 74 



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Fig. 102. Subadult male Pacific walrus in tactual exploration of the bottom of the pool 

 at Marineland, California. While moving head-first along that surface, the animal used 

 his forelimbs as stabilizers and hind limbs for propulsion, while maintaining constant 

 contact of snout and vibrissae (and occasionally the tusks) with the bottom. (Photos by 

 F. H. Fay) 



walruses. The captives spend much of their time exploring the bottom of their 

 pool in a manner that I suspect is comparable to the normal food-search pattern 

 of free-living walruses (Fig. 102). They move forward with the body at an angle 

 of about 10 to 45°, propelling themselves with their hind flippers, often 

 stabilizing with their fore flippers, and maintaining contact of their vibrissae 

 with the bottom. The mystacial vibrissae are perpetually in motion during this 

 process; the eyes usually are closed, and the tusks simply are dragged along. The 

 angle of intercept of the tusks with the bottom is about 20 to 30°, which is 

 consistent with the pattern of striations made by abrasive particles on the tusks of 

 free-living walruses. 



By progressing over the bottom in this manner, the walrus has the sensory 

 receptors (eyes, vibrissae, lips) potentially useful for detecting prey always 

 foremost, where they can function most efficiently. Because the walrus must feed 

 mainly in darkness, the eyes which are comparatively smaller than those of other 

 pinnipeds may be the least important as sensors. The animals probably locate 

 their prey by vibrissal contact. In this mode, much of the feeding of the walrus 

 may be more akin to grazing than to plowing or raking. 



Organisms that reside deep in the sediments and require excavation probably 

 are unearthed by "rooting" with the snout. The pattern of vibrissal abrasion, the 

 greater cornification of the upper edge of the snout (as in swine: Macarian and 



