Seasonality of habitat selection shown to buffer alpine reindeer pastoralism against climate variability

Abstract

Climate‐driven variability of habitat selection of large herbivores has not yet been explicitly analyzed. To this end, we aimed to better understand the climate‐ecological mechanisms behind geographic patterns of reindeer (Rangifer tarandus tarandus) habitat utilization. Our study area comprised of the ranges of Filefjell Reinlag, southern Norway (60°20′–61°20′ N; 8°20′–9°50′ E). We analyzed habitat selection of 20 (± 2) GPS‐collared female reindeer over a period of five years. We examined the mechanistic forces of habitat selection variability by applying a novel stepwise factor analysis approach based on the niche concept. We characterized the governing conditions for inductively delineated seasons and extracted in a first step for each year the seasonal scores of the individual animals on the environmental variables to explain their habitat use. For each season, we then conducted principal component analyses (PCA) to analyze the inter‐annual variability in habitat preferences using the individual scores for the environmental variables per year. In a third step, we fit our potential drivers as vectors onto each seasonal PCA and retained solely significant drivers. Our results reveal complex spatiotemporal patterns of habitat selection that are driven by seasonality, year‐to‐year climate variability, and the choice of individual animals. In contrast to expected similarities between conspecifics, our analyses revealed varying degrees of intra‐species variability and therefore suggest that responses of individual reindeer to climate variability are inconsistent. Moreover, we found annually reoccurring patterns of habitat selection strength during different seasons that help explain coping capacities of reindeer against climate variability. In contrast with our expectations, we detected a very high inter‐annual variability in habitat preferences to be related to governing climatic conditions. Here, we present new evidence for the variability of response mechanisms of reindeer's habitat selection shown throughout different seasons and years that buffer alpine pastoralism against climate variability. Our work contributes to a better understanding of alpine ecological response mechanisms as a key for projections of future responses to climate change.