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
behaviors 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 behaviors 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 behavioral 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.