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Dryad

Multiple drivers of spring migration timing for red deer over the past 16 years in northern Europe

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Nov 14, 2024 version files 43.49 KB

Abstract

The timing of migration is fundamental for species exploiting seasonally variable environments. For ungulates, earlier spring migration is expected with earlier vegetation green-up. However, other drivers, such as access to agricultural farmland and variations in local conditions, are also known to affect migration. We investigated the timing of spring migration for 96 male and 201 female red deer (Cervus elaphus) using a long-term dataset (2005-2020). Overall, the timing of migration was mainly characterised by large individual variability between and within years (95% range from April 6th to June 18th). The spring migration timing was, as expected, later with colder winter and spring conditions (NAO winter and April indices) and later peak vegetation green-up (NDVI), with a 5-day delay in green-up causing a migration delay of 1.2 days. The timing was also influenced by local conditions in summer and winter home ranges. Red deer with higher access to farmland and more variable topography (hence variable plant phenology) in winter delayed migration. Similarly, individuals with higher elevation summer ranges (with delayed onset of plant growth) also delayed migration. Our analyses highlight that the timing of red deer migration is formed by multiple drivers affecting foraging conditions in the landscape, indicative of considerable phenotypic plasticity.