Seasonal strategies differ between tropical and extratropical herbivores

Seasonal diet shifts and migration are key components of large herbivore population dynamics, but we lack a systematic understanding of how these behaviours are distributed on a macroecological scale. The prevalence of seasonal strategies is likely related to herbivore body size and feeding guild, and may also be influenced by properties of the environment, such as soil nutrient availability and climate seasonality. We evaluated the distribution of seasonal dietary shifts and migration across large-bodied mammalian herbivores and determined how these behaviours related to diet, body size and environment. We found that herbivore strategies were consistently correlated with their traits: seasonal diet shifts were most prevalent among mixed feeding herbivores and migration among grazers and larger herbivores. Seasonality also played a role, particularly for migration, which was more common at higher latitudes. Both dietary shifts and migration were more widespread among extratropical herbivores, which also exhibited more intermediate diets and body sizes. Our findings suggest that strong seasonality in extratropical systems imposes pressure on herbivores, necessitating widespread behavioural responses to navigate seasonal resource bottlenecks. It follows that tropical and extratropical herbivores may have divergent responses to global change, with intensifying herbivore pressure in extratropical systems contrasting with diminishing herbivore pressure in tropical systems.