ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 261 



Table 50. Comparison of observed numbers of 1- and 2-year-old young with 

 predicted numbers of calves in two samples of fertile females in the 



Bering Sea. 









Number of 



individuals 









Adult 





1 year 



2 years 



Time 



Location 



female 



Calves^ 



old 



old 



May-June 1954 



St. Lawrence I. 



52 



19 



21 



17 



March-April 1976 



Bristol Bay 



14 



5 



3 



5 



Total 





66 



24 



24 



22 



^Estimated from mean birth rate of 36.7% for adult females (Table 49). 



age in both sexes. Presumably, the mortality of males from natural causes, as 

 well as from the harvests, is greater than that of females at all ages. 



If the survival in the first 2 years is about 80 % , as suggested by Chapskii 

 (1936), and no less than 90% per year for the next 6 or 7 years, as suggested by 

 the low value (0. 16 to 0.2) of F, the female birth rate (Eberhardt and Siniff 1977: 

 Fig. 2), then the recruitment of females from birth to breeding age could be 

 about 40 to 50% . Since the males do not reach maturity until they are about 

 15 years old, well after they enter the harvest, and because their survival rate 

 probably is lower than that of females, I suspect that the recruitment of males 

 from birth to maturity is no greater than about 10 to 20 % . 



Burns (1965) estimated that the net annual increment to the population after 

 natural and harvest mortality was only about 1% in the early 1960's. 

 Conversely, Fedoseev and Gol'tsev (1969) estimated a net loss and concluded 

 that the population was still declining. Probably both of those estimates were 

 very conservative, for the aerial censuses and distributional data suggest a 

 marked increase in population size in recent years. The rate and magnitude of 

 that increase, however, are unknown. 



Outlook 



The Pacific walrus population at present seems to be very large, very produc- 

 tive, and very secure under the current harvest system, but there are a number of 

 uncertainties about its future. Foremost of these, in my opinion, is the 

 biopolitical question of how and by whom the population will be managed. At 

 present, responsibility for management of the population and of the resources 

 with which it interacts rests equally in the hands of the governments of the 

 United States and the Soviet Union, between which there is a considerable com- 

 munication gap. Some progress has been made in recent years in bridging that 

 gap through cooperative interchange under the Marine Mammal Project (V.6.I) 

 of the US-USSR Environmental Protection Agreement of 1972, but the fact 

 remains that each nation still manages the resources within its own jurisdictional 

 boundaries on a unilateral basis. The marine system of the Bering and Chukchi 

 seas and the renewable resources therein do not lend themselves to such parti- 

 tioning. The Pacific walrus population is a prime example, in that it resides in 

 winter mainly in American waters and in summer principally in waters under 



