Table 5. -^Primary causes of death among seal pups within three mortality study areas, St. Paul Island, 4 July to 



15 August 1968 



Total 



132 



100. 



97 



100. 



150 



100. 



379 



100. 



deaths given in table 5 for malnutrition and 

 hookworm disease are based on a total that 

 includes pups unsuitable for examination and 

 pups for which the causes of death were un- 

 determined. 



Malnutrition 



The causes of apparent malnutrition of fur 

 seal pups is not well understood. If death from 

 malnutrition depends on separation of mother 

 and pup and if the extent of separation depends 

 on crowding, then mortality from malnutrition 

 should have been at about the same level since 

 1963. Mortality from malnutrition, however, 

 has varied from Z5 to 61 percent on study area 

 1 of Reef Rookery from 1964 to 1968. We be- 

 lieve that the density of the present population 

 is below the level where density dependent 

 mortality factors are important. Separation of 

 mother and pup owing to crowding is probably 

 not the only cause of malnutrition. Perhaps 

 some disease is involved. For example, a 



disease affecting the mother could stop the 

 flow of milk (agalactia), a condition we have 

 observed in two females captured at the time 

 of parturition. A disease affecting the pup 

 could also interrupt feeding. Any infectious 

 disease with a duration of from 1 to 3 weeks 

 would outwardly manifest itself in the pup by 

 a loss of weight and other condition. Certain 

 types of viruses can cause a loss of appetite 

 (anorexia) without observable gross lesions 

 until those caused by secondary bacterial in- 

 vasion appeared. Actually, most pups that die 

 of apparent malnutrition are emaciated but have 

 no other observable gross lesions except an 

 apparent secondary bacterial enteritis (table 

 6). We have not been able to positively dif- 

 ferentiate between malnutrition caused by di- 

 sease and that caused by simple starvation. 



Hookworm Disease 



"Hookworm disease" refers to the presence 

 of sufficient numbers of the parasite in the 



