264 



NORTH AMERICAN FAUNA 74 



obtain its daily food? Does that bioturbation have a beneficial or detrimental 

 influence on the rest of the fauna in that system? Does it result in a significant 

 release of nutrients that would otherwise be entrapped forever? Why do some 

 walruses feed on the flesh of other marine mammals? Is this a seasonal event or 

 does it take place to some extent in all areas, in all seasons? Do the walruses feed 

 only on carrion, or do they actually pursue and kill other pinnipeds? Do they 

 ever cannibalize their own kind? Are blubber thickness and composition good in- 

 dicators of the kinds and quantities of prey eaten on a seasonal and regional 

 basis? 



Until a great deal more is known about the causes and age-specific rates of 

 natural mortality, the managers will have little hope of accurately estimating the 

 appropriate size of har\'ests. The mortalit}' from predation will be the most 

 difficult to assess, for the animal that is consumed entirely is not readily account- 

 able. Can predation by polar bears be assessed by searching the ice for remains, 

 especially the tough hides which the bears apparently do not eat? Some of the 

 animals that die from other causes eventually drift ashore. Can their age, sex, 

 and cause of death be determined in samples large enough to pro\ide insight into 

 the impacts of those causes on the population? Can counts of sex-age 

 composition, especially of the younger age classes, pro\ide adequate estimates of 

 sur\'i\'orship and recruitment? W^hy is there mass mortalit>' in autumn each year 

 on the Punuk Islands hauling ground and not on other haulouts? 



The managers will require better estimates of population size or relative size 

 and must have more realistic estimates of its composition than are presently 

 available. Further studies of the behavior of the animals, especially of their 

 activity budgets, feeding rhythms, surface: subsurface times, and responses to 

 weather and ice conditions appear to be essential for refinement of census 

 methods and for interpretation of the results. Can the numerical status of the 

 population be monitored more efficiently by annual inventory of animals using 

 traditional hauling grounds? Can a mark-recapture system be developed and 

 implemented to pro\-ide an estimate of population size? Can the indirect bio- 

 logical indicators of population status (such as blubber thickness, serolog}', 

 incidence of disease, reproductive rates, and growth rates) be monitored 

 adequately by sampling the native harvests? How can a reliable estimate of 

 composition of the population be obtained? 



From the ecological aspect, much more information is needed, for example, on 

 the distribution, communit>' structure, standing stocks, and turnover rates of the 

 principal prey. What are their food chains and what are the oceanographic 

 processes on which the\' rely? W^ho are the walrus' principal competitors for 

 those prey? How important are they to the walrus? How do those competitors 

 interact with other components in the system? How does the variation in extent 

 of the winter ice, which is an important substrate for epontic algae, affect the 

 growth and productivity of the walrus' filter- and detritus-feeding prey? How 

 important in general are those epontic algae to the food chains of the walrus' 

 prey? How does the winter ice affect the distribution of walruses, their prey, 

 their predators, and their competitors? How much influence do weather and ice 

 conditions exert on the walrus' success in mating, calving, and survival of the 

 young? 



Clearly, the answers to most of these questions will not be easily obtained. If 



