Our Living Rt'source.s — Alaska 



357 



Walrus Population Estimates 



The point estimates for walrus population 

 size were 221,000 for 1975. 246.000 for 1980. 

 234.000 for 1985. and 201.000 for 1990. Even 

 though confidence intervals of these estimates 

 were large, these estimates are considered the 

 best infomiation available to assess the status 

 and trends of the Pacific walrus (Hills and 

 Gilbert 1994). Estimates from sea ice exceeded 

 those from land haul-outs except during 1990. 

 when the ice pack receded much farther north 

 and over deeper water than in most years. 

 Because most of the large land haul-outs were 

 in Russia, estimates there are higher than in the 

 Llnited States. Although these data indicate a 

 general decline in numbers of walrus between 

 1975 and 1990, some biologists question the 

 validity of this apparent decline (Hills and 

 Gilbert 1994). Other researchers believe the 

 population may be declining, based on various 

 biological indices (Fay et al. 1989). 



References 



Estes. J.A.. and J.R. Gitbert. ]978. Evaluation of an aerial 

 survey of Pacific walruses {Odobenus wsmarus diver- 

 gens). Journal Fisheries Research Board Canada 

 35:1130-1140. 



Estes. J. A., and V.N. Gol'tsev. 1984. Abundance and distri- 

 bution of Pacific walrus. Odobenus rnsmarus divergens: 

 results of the first Soviet-American joint aerial survey, 

 autumn 1975. Pages 67-76 in F.J, Fay and G.A. 

 Fedoseev, eds. Soviet-American cooperative research on 

 marine mammals. Vol. 1: Pinnipeds. National Ocean- 

 ographic and Atmospheric Administration Tech. Rep., 

 National Marine Fisheries Ser\'ice 12. 



Fay, F.H. 1982. Ecology and biology of the Pacific walrus. 

 Odiihenus rosmariis divergens Illiger North American 

 Fauna 74:1-279. 



Fay, FH., B.P Kelly, and J.L. Sease. 1989. Managing the 

 exploitation of Pacific walruses: a tragedy of delayed 

 respon.se and poor communication. Marine Mammal 

 Science 5:1-16. 



Gilbert. J.R. 1986. Aerial survey of Pacific walrus in the 

 Chukchi Sea. 1985. U.S. Fish and Wildlife Service, 

 Anchorage. AK. 41 pp. 



Gilbert. J.R. 1989. Aerial census of Pacific walruses in the 

 Chukchi Sea, 1985. Marine Mammal Science 5:17-28. 



Gilbert. J.R., G.A. Fedoseev. D. Seagars, E. Razlivalov. and 

 A. Lachugin. 1992. Aerial census of Pacific walrus. 

 1990. U.S. Fish and Wildlife Service Admin. Rep. 

 R7/MMM92-I.33pp. 



Hills. S., and J.R. Gilbert. 1994. Detecting Pacific walrus 

 population trends with aerial survey — a review. 

 Transactions of the North American Wildlife and Natural 

 Resource Conference 59. Wildlife Management Institute. 

 Washington, DC. In press. 



Johnson, A., J. Bums, W. Dusenberry, and R. Jones. 1982. 

 Aerial survey of Pacific walrus, 1980. U.S. Fish and 

 Wildlife Service, Anchorage, AK. 32 pp. 



For further information: 



Gerald W. Gamer 



National Biological Service 



Alaska Science Center 



1011 E. Tudor Rd. 

 Anchorage, AK 99503 



The Mentasta caribou (Rangifer taramliis) 

 herd, a small herd that lives in and around 

 Wrangell-St. Elias National Park and Preserve. 

 Alaska, experiences population trends and man- 

 agement problems that are typical of many 

 mountain herds in central Alaska and the Yukon 

 Territory of Canada. Traditionally, the herd has 

 been important for sport and subsistence hunt- 

 ing, but a recent decline in numbers led to sus- 

 pension of hunting in 1992. The Alaska 

 National Interest Lands Conservation Act 

 authorizes the National Park Service to allow 

 subsistence hunting throughout Wrangell-St. 

 Elias. and sport hunting on preserve lands, pro- 

 vided that hunting is consistent with sound 

 wildlife management principles and conserva- 

 tion of natural and healthy populations. Even 

 though the National Park Service allows hunt- 

 ing, other agency mandates do not allow preda- 

 tor control or habitat management to enhance 

 declining populations for hunting. 



Sound information on caribou populations, 

 gathered every year, is used to determine when 

 hunting seasons are allowed and how many 

 caribou can be taken by hunters. The collection 

 of reliable data will help minimize contTicts 

 between the dual objectives of providing hunt- 

 ing opportunities and maintaining natural char- 

 acteristics of wildlife populations. Infonnation 

 on wildlife populations in national parks also 

 provides important insights on natural popula- 

 tion fluctuations for comparison with more 



actively managed wildlife on adjacent lands. 



Biologists have monitored population size 

 and composition of the Mentasta herd routinely 

 since 1973 to provide basic information for 

 management. They expanded monitoring and 

 research in 1992 to improve their understanding 

 of population-limiting factors during a period of 

 rapid population decline. 



Surveys of the Caribou Herd 



Biologists have estimated the size of the 

 Mentasta herd nearly each year since 1973 from 

 aerial surveys conducted after the calving sea- 

 son. During late June, caribou congregate in 

 high-mountain habitats or snow fields, where 

 they are most readily visible from airplanes, and 

 are counted by biologists. 



Biologists also determine the population 

 composition of the herd twice annually: after 

 calving season in late June and during breeding 

 season in early October. They classify caribou 

 as calves, cows, or bulls. The counts in late June 

 provide an index of early calf survival; counts in 

 early October provide an index of summer sur- 

 vival of calves and proportions of bulls in the 

 population. 



In 1992 and 1993, biologists determined 

 birth rates of cows to see whether low calf-to- 

 cow ratios in late June resulted from low pro- 

 ductivity. They determined birth rates by 

 inspecting cows at close range from a helicopter 



Mentasta 

 Caribou Herd 



by 



Kurt Jenkins 

 National Biological Service 



