ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



7 



shoulders of the adult males (Allen 1880; Pedersen 1962). Probably, there are 

 other differences that have not yet been recognized. 



Distribution and Migrations 



Nearly the entire life of the Pacific walrus is spent at sea, though perhaps no 

 more than two-thirds of it is spent in the water (Fay and Ray 1968). Walruses 

 frequently come out of the water (haul out) onto ice or land to rest and, in 

 certain seasons, to bear their young and to molt. The usual place for hauling out 

 is on snow-covered ice floes, rather than on land, apparently by preference 

 (Nikulin 1947). Keeping mainly to the moving pack ice, most of the population 

 spends the winter in the Bering Sea and the summer in the Chukchi Sea. The 

 regularity of the migrations northward in spring and southward in autumn must 

 have been evident to Eskimos of the Bering Strait region for thousands of years. 



The pattern of those migrations is known only in a general way from 

 compilation of reports of sightings from land, from icebreaking ships, and from 

 aircraft. The first major attempt to analyze and describe that pattern was by 

 Belopol'skii (1939), based mainly on his observations in eastern Chukotka. A con- 

 siderable volume of additional sightings from other locations was added by 

 Nikulin (1941), who spent five summers with the Soviet sealing fleet in the Far 

 East. Brooks (1954) and Burns (1965) briefly redescribed the migrations on the 

 basis of the Soviet data and their own observations in the Bering Strait region 

 and northward to Barrow. 



A large amount of new data has become available in the years since Brooks' 

 and Burns' reports were prepared. Both the United States and the Soviet Union 

 have conducted numerous aerial surveys of the walrus' habitat since 1958, in 

 efforts mainly to assess the numerical status of the population. Research ex- 

 peditions into the habitat of the walrus via iceworthy vessels also have been more 

 numerous. Thus, the information now available provides a much clearer view of 

 the movements of the population than was available in the 1950's, when I began 

 my work. However, as will be seen, some major gaps in our knowledge of annual 

 movements still exist, mainly for the autumn and winter months and during the 

 spring migration. It is not likely that all of those gaps will be filled very quickly, 

 for the short daylight in winter and inclement weather in autumn interfere with 

 aerial and shipboard observation. 



I have summarized the data available to me concerning positions and numbers 

 of walruses sighted in each month. These sightings were compiled from pub- 

 lished records from 1930 to 1978 and from unpublished records up to 1979. These 

 span a 50-year period in which the population apparently changed from a high 

 to a very low number, then back to a high number again. The greater part of the 

 sightings were recorded during the latter half of that period. 



My sources of published records were Chech ulin (1936), Belopol'skii (1939), 

 Collins (1940), Freiman (1941), Nikulin (1941, 1947), Wilke (1942), Porsild 

 (1945), Lantis (1946), Rainey (1947), Brooks (1953, 1954), Fay (1957), Manville 

 (1961), Fedoseev (1962, 1966), Yablokov and Bel'kovich (1963), Burns (1965), 

 Anonymous (1965), Harington (1966), Johnson et al. (1966), Krylov (1966fl, 

 1968), Gol'tsev (1968), Kosygin and Sobolevskii (1971), Watson and Divoky 

 (1972), Stirling (1974), Tomilin and Kibal'chich (1975), Pinigin and Prianish- 



