340 



Alaska — Our Living Resources 



50- 



72 77 79 



83 

 Year 



87 



92 



Fig. 3. Pholocensiis results for the 

 Porcupine canhou {RaiiKifer taraii- 

 diis) herd. 1972-92. 



For further information: 



Thomas R. McCabe 



National Biological Service 



Fairbanks Field Station 



Box 15 



101 12th Ave. 



Fairbanks. AK 99701 



Predator.s 



We determinetJ the number of brown bears 

 on the Coastal Plain portion of the refuge from 

 densities recorded during extensive aerial sur- 

 veys in 1983. Subsequent trends in the popula- 

 tion were based on composition counts and sur- 

 vival estimates obtained from monitoring radio- 

 tagged bears. 



We located wolf dens and packs by monitor- 

 ing radio-tagged animals and aerial surveys. In 

 1984. we made a minimum estimate of the pop- 

 ulation by recognizing individual wolves. We 

 based trends in pack size and composition on 

 ground observations collected at the den site. 



We completed aerial surveys of golden eagle 

 nest sites twice each year from 1988 to 1990 to 

 monitor trends in nest occupancy and nestling 

 production. 



Status of the Arctic Ecosystem 



Caribou 



The PCH increased from an estimated 

 lOO.OOO animals in 1972 to peak at 178.000 in 

 1989. then dropped to 160.000 in 1992 (Fig. 3). 

 The growth rate averaged 4.89f/year from 1979 

 to 1989. Since 1989 the population has either 

 stabilized or declined. Ratios of calves to 100 

 cows ranged from a low of 38 in 1971 to a high 

 of 73 in 1983. This trend in herd productivity 

 generally agrees with the trends in population 

 growth. 



We observed no consistent trends in the esti- 

 mates of annual survival of adult females. The 

 population dynamics of the PCH aie similar to 

 the longer term cycles observed in other barren- 

 ground caribou herds. 



Muskox 



The muskox population on the Coastal Plain 

 increased an average of 20%/year (Fig. 4). After 

 1986 numbers of muskox in ANWR decreased 

 and then stabilized at about 350 animals, and 

 numbers of muskox east and west of the refuge 

 increased. In 1993 we observed 720 muskox, 

 including 370 on the ANWR Coastal Plain. 



Annual productivity for the muskox popula- 

 tion on ANWR has averaged about 48 calves 

 per 100 cows since 1985. In the highly produc- 

 tive years of 1984, 1985, and 1988, calf-to-cow 

 ratios were greater than 70:100 and calves 

 accounted for more than 21 % of the total popu- 

 lation. Age at death for five known-age cows 

 averaged 13.8 years (range: 9-19) and annual 

 survival averaged 88% for adult cows and 77%- 

 78% for yearlings and calves. Changes in distri- 



bution occuned during years following winters 

 in which biologists observed lower productivity 

 and survival of young animals and adult cows. 

 The dynamics and behavior of the population 

 are typical of animals reintroduced into suitable 

 habitat. 



Predators 



In 1983 we estimated that there were 108 

 brown bears on the north slope of ANWR. 

 Between 1983 and 1993 estimates of survival 

 and reproductive rates of the bear population 

 were stable and distribution and movements of 

 bears were consistent. This consistency sug- 

 gests that the bear population is stable. 



In 1984 we estimated that a minimum of 34 

 wolves occurred on the north slope of ANWR. 

 A mean litter size of 4.2 during 1988-90 was 

 consistent with the 3.0 reported for ANWR in 

 1984 and 4.3 in 1985. Population size appears 

 stable. 



ANWR West of ANWR — NE Canada 



500- 



Year 



Fig. 4. Growth and stabilization of the pioneering muskox 

 (Ovihos mosclmtus) population within the Arctic National 

 Wildlife Refuge and adjoining areas. 



Between 1988 and 1990 we observed 31 

 nesting attempts by golden eagles on the noilh 

 slope of the ANWR between the Canning and 

 Kongakut rivers. Twenty-seven of the 31 (87%) 

 breeding pairs produced 33 young, resulting in 

 1 .22 young per successful pair. The number of 

 young remained constant from 1988 to 1990, 

 suggesting that the ANWR eagle population is 

 also stable. 



Reference 



McCabe. T R.. D B. Griffith. N.E. Walsh, and D.D. Young. 

 1992. Terrestnal reseaich: 1002 Area. Arctic National 

 Wildlife Refuge. Interim Report, 1988-1990. U.S. Fish 

 and Wildlife Sen'ice. Anchorage, AK. 432 pp. 



