Populations on the limits: survival of Svalbard rock ptarmigan

Predictable variation in demographic patterns among populations inhabiting extreme environments can be used to direct common management actions. Ptarmigan and other grouse are ecologically important herbivores in Arctic and alpine areas, but survival estimates are lacking for many harvested populations. This hampers more detailed assessment of how this key determinant of population growth rate is related to environmental variability and whether there is predictable between–population variation. In this article, we estimated apparent survival by age and sex of the endemic high-Arctic Svalbard rock ptarmigan (Lagopus muta hyperborea) using a 6-year mark–recapture dataset from the west coast of Spitsbergen (1980–1986). Second, we tested whether seasonal climatic variability explained temporal variation in adult survival rates. Within the Svalbard rock ptarmigan population, annual adult survival did not differ between the sexes, but varied among locations. Temporal variation in adult survival was limited and could not be explained by climatic variability. A review of inter-population comparisons of vital rates (survival and reproduction) of rock ptarmigan populations suggested that the high-Arctic, low-elevation Svalbard rock ptarmigan populations resemble their low-Arctic counterparts, and settles at the ‘low survival–high reproduction’ end of the ‘slow–fast continuum’. The demographic traits of high-Arctic ptarmigan contrast with the ‘high survival–low reproduction’ of rock ptarmigan populations at low latitudes and high elevations. Our study demonstrated that spatial variation in survival rates exists both within and between Svalbard rock ptarmigan populations. We suggest that further studies focus on ecological gradients underlying the spatial variation of life history and thus shape the population dynamics and long-term resilience.