228 



NORTH AMERICAN FAUNA 74 



Fig. 130. Intramuscular hemorrhage in the neck and shoulders of a 6-month-old walrus 

 calf that died from intraspecific trauma. Right dorsolateral view with skin, blubber, and 

 superficial musculature removed. Scale in centimeters. (Photo by B. P. Kelly) 



Parasitism 



Walruses appear to be the least affected of all pinnipeds by parasites 

 (Deliamure 1955; Yurakhno and Treschev 1972). Brooks (1954) and Loughrey 

 (1959) concluded that parasitism does not seem to be an important cause of 

 illness or death in any walrus population at the present time. Sixteen species of 

 parasites have been recorded from the Pacific walrus, and a few of them may be 

 pathogenic. 



Ectoparasites 



All walruses are infested by the anopluran louse Antarctophthirus trichechi 

 (Boheman), which resides in the skin folds over the entire head, body, and 

 appendages, as well as in the external ear canals and about the base of the 

 mystacial vibrissae. This louse is host-specific, occurring only on walruses. 

 Although usually abundant, it does not seem to cause more than mild irritation 

 under natural conditions. Much of the rubbing and scratching that walruses 

 engage in probably is in response to these parasites (Miller 1975^?). Anopluran 

 lice of related species in other pinnipeds are suspected to be vectors of infection 

 by two genera of filariid nematodes that inhabit the circulating blood as larvae 

 and the right ventricle of the heart as adults (e.g. , see Taylor et al. 1961). Neither 

 of those nematodes, however, has been found as yet in any walruses. 



