Dynamics of Moose Populations in Northeastern Alberta

Abstract

Intensive studies of moose (Alces alces) were conducted on a 25,000-km2 study area in northeastern Alberta from January 1976 to June 1978. Sixty-six moose were radio-collared and color-marked and another 8 were color-marked only. The population was either stationary or slowly declining; an estimate of 4,595 (0.18/km2) was obtained for the entire study area in winter 1977-78. The proportion of yearlings in the population increased between winter 1975-76 and 1976-77, the result of higher reproduction and/ or calf survival in 1975-76. Our best estimate of the combined yearling and adult sex ratio was 30:70. There was an inverse relationship (r2 = 0.62) between age of radio-collared bulls and dates of antler drop. Calf production as indexed by calf-cow ratios was similar in spring (May-Jun) 1976 and 1978, but fall ratios were higher in 1977 than 1976. Calves constituted 30% of the 1975-76 winter population, 18% in 1976-77, and 20% in 1977-78. The annual survival rate of calves of radio-collared cows was 0.27. Survival of calves was lowest in the first month of life (0.61) and rose in subsequent months (0.95). An estimated 29% of calf losses were due to wolf (Canis lupus) predation. The annual survival rate of radio-collared yearlings and adults averaged 0.75. A 2nd estimate of 0.76-0.77 was obtained independently from demographic and kill data for the entire study-area population in 1977-78. Hunting and wolf predation were the main causes of mortality among yearlings and adults; wolves consumed an estimated 23-24% of those dying in 1977-78. Moose were largely absent in winter from the Birch Mountains and the Jackpine Area north of the Firebag River. Seasonal shifts between winter and summer home ranges were made by 34 (76%) of 45 moose; 13 (38%) of these movements exceeded 20 km. No differences (P > 0.05) in homerange size were found among sexes or seasons. Three distinct periods of increased movement among bulls were observed: April-May, September-October, and December-January. Cow movements were more leisurely and less well defined. Spring (May-Jun) calf-cow ratios among radio-collared cows >3 years old averaged 88:100. Visual observations of radio-collared moose suggested that: (1) moose were least gregarious from April to August, (2) cow-bull associations increased in September and lasted through November, (3) in November young bulls (1.5-2.5 years old) were associated with cows more than were older bulls, (4) bull association with other bulls increased in November, and (5) cows with calves associated with other adult moose less than did single cows. Uplands were used more than lowlands from June through September, and upland use increased in October. Lowland use rose in November and December, more so by bulls than cows, but decreased from January to March as snow depth increased. Snow depths were greatest within lowland cover types. Lowland use on winter home ranges (Dec-Mar) was related (r2 = 0.60) to availability. Decreased snowfall in winter 1976-77 resulted in increased lowland use in February and March. Lowland use rose markedly and peaked in April and May. If there are critical habitats for moose, they are likely the open lowlands that apparently provide the first high-quality food in spring. The rate of exploitation of moose in this region likely cannot be raised without producing a major population decline. The most promising means of increasing the allowable harvest would be to reduce the high early mortality of calves. J. WILDL. MANAGE. 45(3):573-597 Commercial production of oil from the tar sands of northeastern Alberta began in 1964, upon completion of an extraction plant and refinery by Great Canadian Oil Sands Ltd. This 50,000-barrel/day facility was joined in 1978 by a 127,000-barrel/day plant of Syncrude Canada Ltd. At least one additional plant and a new townsite are planned by 1984. The long-term impacts of such industrialization and its support services on wildlife and other renewable natural resources within this 23,300-km2 region (Fig. 1) could be highly detrimental. Establishment of the Alberta Oil Sands Environmental Research Program (AOSERP) in 1975 reflected public concern over the potential environmental consequences of oil sands development. The present study, part of AOSERP, was conducted from January 1976 through June 1978. Its objective was to determine J. Wildl. Manage. 45(3):1981 573 This content downloaded from 157.55.39.78 on Mon, 20 Jun 2016 07:30:09 UTC All use subject to http://about.jstor.org/terms 574 DYNAMICS OF MOOSE IN ALBERTA* Hauge and Keith