Woodland Caribou Relative to Landscape Patterns in Northeastern Alberta

Abstract

From 1991 through 1994, 65 adult woodland caribou (Rangifer tarandus caribou) were radiocollared and monitored across 20,000 km 2 of northeastem Alberta. Adult survival averaged 0.88 ± 0.03, and did not differ among years. Calf survival was 18 calves/100 cows in March of both years it was measured, with calves composing a mean of 9.0% of the March populations. Highest calf mortality occurred during the first month of life. The population rate-of-increase, r, was -0.08 (A = 0.92), suggesting the population was declining. Caribou locations were restricted to peatlands, with 98.7% of locations falling within the 5 fen complexes in the study area. There was little permanent movement (5% of individuals over 4 yr) among fen complexes. Multi-year home ranges (100% minimum convex polygon; MCP) averaged 711 km 2 , with the size of individual home ranges (HR) correlated with the area of fen complexes. Summer HRs were smaller than winter HRs, and smaller for females than males in summer, but not winter. Locations were further from fen/upland boundaries in winter than in summer, and further from fen/upland boundaries than random points within fens in both seasons. Movement rates were highest in winter and lowest in summer, and did not differ between sexes. There was a negative correlation between movement rate and snow depth at month-end. Monthly trends in group size paralleled those in movement rates, while group composition was relatively stable throughout most of the year. Trends in group size, movement, and spatial distribution suggest caribou increased spacing among themselves during summer, and were more concentrated during winter. The study area consisted of 2 different landscapes, varying in the amount and configuration of fen patches. When we compared caribou biology between the 2 areas, we found lower calf survival and smaller home ranges in the landscape with smaller fen patches and a higher proportion of upland.