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ABSTRACT Modern African ungulates navigate seasonal variation in resource availability through diet‐switching (primarily mixed‐feeders) and/or migrating (primarily grass grazers). These ecological generalisations are well‐documented today, but the extent to which they apply to the non‐analog ecosystems of the Pleistocene are unclear. Drawing from serially‐sampled stable isotope measurements from 18 Kenyan large herbivore species from the Last Glacial Period (LGP), we evaluate how diet, diet‐switching, and migration compare to observations from present‐day settings. We find a higher grazing signal in most LGP species and a greater magnitude of diet‐switching than in the present. Additionally, we find that the relationships between grass intake, migration, diet‐switching, and body size during the LGP were unlike those observed today. This establishes a revised paleoecology of LGP herbivore communities and highlights that LGP herbivores were behaviourally non‐analog. Our results imply that ecological observations from present‐day settings offer an incomplete perspective of herbivore‐environment interactions. 

Abstract Though herbivore grass dependence has been shown to increase with body size across herbivore species, it is unclear whether this relationship holds at the community level. Here we evaluate whether grass consumption scales positively with body size within African large mammalian herbivore communities and how this relationship varies with environmental context. We used stable carbon isotope and community occurrence data to investigate how grass dependence scales with body size within 23 savanna herbivore communities throughout eastern and central Africa. We found that dietary grass fraction increased with body size for the majority of herbivore communities considered, especially when complete community data were available. However, the slope of this relationship varied, and rainfall seasonality and elephant presence were key drivers of the variation—grass dependence increased less strongly with body size where rainfall was more seasonal and where elephants were present. We found also that the dependence of the herbivore community as a whole on grass peaked at intermediate woody cover. Intraspecific diet variation contributed to these community‐level patterns: common hippopotamus (Hippopotamus amphibius) and giraffe (Giraffa camelopardalis) ate less grass where rainfall was more seasonal, whereas Cape buffalo (Syncerus caffer) and savanna elephant (Loxodonta africana) grass consumption were parabolically related to woody cover. Our results indicate that general rules appear to govern herbivore community assembly, though some aspects of herbivore foraging behavior depend upon local environmental context.