Dynamics of moose populations in the AOSERP study area in northeastern Alberta

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  • Intensive studies of moose were conducted on a 25 000 km study area in northeastern Alberta from January 1976 to June 1978. Sixty-six moose (Alces alces) were radio-collared and another eight were colour-marked only. The population is either stationary or slowly declining. An estimate of 4595 (0.18/km2) for the entire study area was obtained in the winter of 1977-78. Moose were largely absent in winter from the Birch Mountains and the jack pine area north of the Firebag River. There was a significant increase in the proportion of yearlings in the population between the winters of 1975-76, as a 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 a significant inverse relationship (r2 = 0.62) between age of radio-collared bulls and dates of antler drop. 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 significant differences in home-range size were found between sexes and 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-June) calf-cow ratios among radio-collared cows >3 years old averaged 88:100. Calf production as indexed by calf-cow ratios was similar in spring (May-June) 1976 and 1978, but autumn ratios were higher in 1977 than 1976. Calves constituted 30% of the winter populations in 1975-76, 18% in 1976-77, and 20% in 1977-78. The annual survival rate of calves of radio-collared cows was 0.27. Survival of these 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 predation. The annual survival rate of radio-collared yearlings and adults averaged 0.75. A second estimate of 0.76 to 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. Wolves consumed an estimated 61 to 66% of the yearlings and adults dying in 1977-78. Visual observations of radio-collared moose suggested that: (1) moose were leas~ gregarious from April to August; (2) a significant increase in cow-bull associations occurred in September and lasted through November; (3) in November young bulls (1.5 to 2.5 years old) were associated with cows more than were older bulls; (4) bull association with other bulls increased significantly in November; and (5) cows with calves associated with other adult moose significantly less than did single cows. Uplands were used more than lowland from June through September, but upland use increased significantly 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 covertypes. Lowland usage on winter home ranges (December-March) was significantly related (r2 = 0.60) .to availability. Decreased snowfall in winter 1976-77 resulted in increased lowland usage in February and March. Lowland use rose markedly and peaked in April and May. If there are \"critical\" habitats for moose, they are 1ikely the open lowlands which apparently provide the first high quality food in spring. The rate of exploitation of moose in this region cannot likely 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.

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