Calving Phenology and Associated Habitat Selection of Caribou in West Greenland

Sammanfattning

Reproductive ecology shapes population dynamics of large herbivores, with neonatal survival closely tied to maternal behavior during and after parturition. In cold seasonal environments, females must time calving with snow melt, balancing access to high-quality forage with environmental risks. In this study, I examined calving phenology, habitat selection, and spatial aggregation of barren ground caribou (Rangifer tarandus groenlandicus) in West Greenland during the calving and post-calving season. Using telemetry data from 38 females (2024-2025), I identified calving events and modeled habitat selection across multiple spatial scales (populational, subregional, and individual home range) with resource selection functions, from which a habitat suitability map was derived. Results showed a consistent median calving date across both years (29 May), despite different spring conditions. The proportion of females with versus without detected calving differed between years (60% in 2024; 30% in 2025). At the population scale, females selected for advanced spring green-up, higher elevation, and greater grassland cover; at the subregional scale, selection favored intermediate elevations and higher fen cover; and the individual home range scale, females selected for advanced spring green-up, higher elevations, greater grassland cover and avoided fens. The habitat suitability map showed a clear continentality gradient with higher suitability inland. Females aggregated more in spring, though the timing did not align with median calving dates. The different selection patterns found across scales highlight the importance of considering spatial scales for caribou management in West Greenland. This study further underscores the vulnerability of caribou to climate change, as calving timing showed limited flexibility, and important habitats like grassland and fen are threatened by shrubification.