Long-Term Control of Peary Caribou Numbers by Unpredictable, Exceptionally Severe Snow or Ice Conditions in a Non-equilibrium Grazing System
Keywords: Arctic Canada, population dynamics, Rangifer tarandus pearyi, weather-related density-independent population crashes
AbstractThe number of Peary caribou (Rangifer tarandus pearyi) on the Queen Elizabeth Islands, Canadian High Arctic, is at an all-time known low. Yet some populations are still hunted, and there is no adequate monitoring program in place to determine the consequences. We evaluate information from the Peary caribou population on the south-central Queen Elizabeth Islands as a standard for an accurate and realistic assessment of what controls Peary caribou population dynamics. Between 1973 and 1997, major population crashes related to severe winter or spring weather are known to have occurred on the south-central Queen Elizabeth Islands in four caribou-years (i.e., 1 July–30 June). Population losses were 67% in 1973–74, 33% in 1994–95, 78% in 1995–96, and 83% in 1996–97. There is no evidence for direct density-dependent responses during either the favorable weather years of population growth or during any one of the years with a disastrous die-off. It appears that Peary caribou on the Queen Elizabeth Islands are living in a non-equilibrium grazing system driven mainly by abiotic factors (emergent properties), particularly by exceptionally unfavorable snow or ice conditions. Changing levels of predation by the High Arctic gray wolf (Canis lupus arctos) compound the uncertainty. In this High Arctic ecosystem, non-equilibrium–governed population dynamics plus wolf predation represents an appropriate conceptual model for Peary caribou populations on the Canadian High Arctic islands. The application of our findings to decision making, together with an adequate monitoring program by the responsible agencies, would promote the biological management and ecological conservation of Peary caribou on the Queen Elizabeth Islands.