Factors affecting timing of seasonal migration by roe deer (Capreolus capreolus)

Abstract: Roe deer (Capreolus capreolus) live in diverse environmental conditions due to their wide distribution. Because of their high variety of living conditions it is common that some individuals in a population have different summer and winter areas. These areas are generally the same over the years and the migrations between these areas occur in spring and fall. The timing and distance of these seasonal migrations was the main focus of my study. Timing of migration can be affected by various factors and by studying the impact of age, sex, seasonal phenology (determined by the Normalized Difference Vegetation Index, NDVI), winter severity, temperature, and migration distance this study investigated the relative importance of these factors in affecting timing of seasonal migration. This study showed that age and seasonal phenology were the main factors affecting the timing of seasonal migration in spring with earlier departure in early springs and by older animals. Furthermore, shorter distance between seasonal areas resulted in a greater variation in the timing of seasonal migration, both between individuals but also within the same individual for animals that were followed during several years. Age and seasonal phenology were the main factors affecting timing of seasonal migration also in the fall. However, in addition sex was also affecting the timing of migration in fall. Overall, variation in the timing of seasonal migration was greater in fall than in spring and male roe deer stayed at the summer ranges longer than females. Females, especially those who migrated >10 km, returned to winter areas earlier than short-distance migrants.