ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



29 



including eastern St. Lawrence Island, Nome, and King Island, may be taken in 

 most years mainly from the animals that have wintered in Bristol Bay. Certainly 

 the spring harvests at Gambell and eastern Chukotka are mainly from the St. 

 Lawrence wintering concentration. At Diomede and points north, the harvests 

 probably are of animals from both concentrations, for the distributional data 

 suggest mixing of the two in the Chukchi Sea. Since the animals from both 

 wintering concentrations appear to transcend international boundaries and to be 

 cropped by both the Soviet Union and the United States, the case for bi-national 

 research and management of the Pacific walrus population is strong. 



More current, definitive distributional information clearly is needed, 

 particularly in November to February and in May and June. Also needed is an 

 assessment of the site fidelity of animals in the wintering concentrations and their 

 respective representation in the apparent clumps of animals in the summering 

 areas. This will require not only intensive distributional surveys but large-scale 

 marking of animals in the wintering areas, as well, to trace their migrations and 

 their relative contributions to local harvests along the migration routes. The 

 areas in which mating and calving take place also need to be delineated. These 

 activities can best be done on a cooperative basis by the two countries. 



General Morphology and Growth 



General descriptions of the major physical characters of walruses have been 

 presented in several reports (e.g.. Brooks 1954; Mansfield 1958a; Loughrey 1959) 

 and will not be repeated here. However, I have investigated some of those 

 characters in much greater detail than ever before, and because I regard the 

 understanding of them as critically important for dispelling some myths and 

 developing new points of view, I shall redescribe a few of them in this and the 

 next two chapters. These include body size and weight, growth of the 

 reproductive organs, characteristics of the skin and hair, and the development 

 and form of the dentition. Because, in each instance, the information is related to 

 the age of the individual, a few words on the method of age determination are 

 necessary. 



Age Determination 



Before the development of modern methods of age determination for walruses, 

 the Eskimos and other indigenous people of the North perceived that these 

 mammals were long-lived and that their physical characteristics changed with 

 age. To describe this, they evolved an elaborate traditional nomenclature that 

 was useful for classifying the animals for their purposes into several broad groups 

 by sex and relative age. Early in the present century, Soviet biologists recognized 

 the need for greater objectivity and precision in age determination that would 

 allow them to obtain the demographic information required for sustained-yield 

 management of walruses. Their efforts in the North Pacific region were 

 pioneered by Belopol'skii (1939), who observed that the tusks of these animals 

 grow persistently at the rate of about 1 cm per year, and that the younger age 

 classes, at least, could be recognized on the basis of the length of their tusks. 



