The global climate change processes are expected to impact African savanna ecosystems in their ecological functionality and availability of food resources for herbivores. To understand the feeding responses of large savanna herbivores placed to space-constrained and two environmentally distinct (semi-arid versus sub-humid savanna) conditions, we investigated the diet quality of five species living in a mixed community of species native and non-native for the West African savanna and compared them between the two sites as a proxy for a potential ecosystem shift due to climate change. Grazers and mixed feeders maintained diet quality in most nutrients at similar levels, while browser’s diet had lower nitrogen and fibres, specifically lignin, and more calcium in semi-arid savanna. Our findings suggest that adaptation to different ecosystems with no possibility to leave the area required changes in feeding behaviour across feeding types to maintain diet quality, especially mixed feeders escaped the competition with zebras for grasses in sub-humid savanna by switching to browse. Pure browser experienced reduced diet quality in drier environment and may potentially become susceptible to ecosystem changes. Conservation strategies should facilitate both, animals’ adequate behavioural responses together with nutritional resilience in changing savanna landscapes.