Résumé
Animals exhibit a diversity of movement tactics [1]. Tracking resources that change across space and time ispredicted to be a fundamental driver of animal movement [2]. For example, some migratory ungulates (i.e.,hooved mammals) closely track the progression of highly nutritious plant green-up, a phenomenon called‘‘green-wave surfing’’ [3–5]. Yet general principles describing how the dynamic nature of resources determinemovement tactics are lacking [6]. We tested an emerging theory that predicts surfing and the existenceof migratory behavior will be favored in environments where green-up is fleeting and moves sequentiallyacross large landscapes (i.e., wave-like green-up) [7]. Landscapes exhibiting wave-like patterns of greenupfacilitated surfing and explained the existence of migratory behavior across 61 populations of four ungulatespecies on two continents (n = 1,696 individuals). At the species level, foraging benefits were equivalentbetween tactics, suggesting that each movement tactic is fine-tuned to local patterns of plant phenology. Fordecades, ecologists have sought to understand how animals move to select habitat, commonly defininghabitat as a set of static patches [8, 9]. Our findings indicate that animal movement tactics emerge as a functionof the flux of resources across space and time, underscoring the need to redefine habitat to include itsdynamic attributes. As global habitats continue to be modified by anthropogenic disturbance and climatechange [10], our synthesis provides a generalizable framework to understand how animal movement willbe influenced by altered patterns of resource phenology.