ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 231 



Fig. 131. Photomicrograph of a section through the Hver of a walrus, showing fibrous 

 thickening of a bile duct. The wall of the duct (W) is about 2 mm thick, which is about 

 20 times the normal thickness for a duct of this size. This condition apparently was an 

 inflammatory reaction to presence of the trematode Orthosplanchnus fraterculus. (Photo 

 by S. M. Coulthard) 



by the ring-like lesions. That animal, nonetheless, appeared to be normally 

 active and healthy in all other respects. 



Pulpitis of the Tusks 



Bacterial infections of the pulp of the tusks occurs commonly in walruses 

 reared in captivity; I have seen only seven cases in free-living walruses of perhaps 

 2,000 specimens examined. At least two of these were attributable to bullet 

 wounds (fragments of the bullet were found in the site); three of the others were 

 certainly identified as having been caused by other traumatic agents, possibly 

 tusk strikes by other walruses. In six cases, purulent exudate was draining to the 

 exterior through one or more perforations of the maxilla near the proximal end of 

 the tusk; in three cases there was extensive periodontitis, as well. The principal 

 effect of such infections seems to be shedding of the affected tusk, which may 

 have grave social consequences but probably is of little importance otherwise. 

 The possibility of spread of the infection to other organs, for example, by 

 inhalation of the purulent exudate, may have more lethal consequences. In an 

 adult male and an adult female with abscessed tusks, the principal drainage from 

 the abscess was through a hole in the wall of the left nasal passage, whereby 

 direct inhalation of the exudate would have been unavoidable. I examined only 

 the head of the male but was able to perform a complete necropsy of the female, 



