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Impacts of large herbivores on savanna plant communities: Towards predictive models of herbivore selectivity and plant response

Abraham, Joel1; Stahl, Maria2; Kurukura, Samson3; Ali Hassan, Abdikadir3; Goheen, Jacob4; Palmer, Todd5; Kartzinel, Tyler6; Pringle, Rob1

Research facility: Mpala Research Center and Wildlife Foundation
Published Apr 06, 2026 on Dryad. https://doi.org/10.5061/dryad.41ns1rntq

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Abstract

Large herbivores are among the most ecologically influential and extinction-prone animals. Megaherbivores in particular radically alter vegetation. Few studies have tried to predict the impacts of herbivores—or their loss—on plant species composition and community structure. First principles suggest that preferred plants should be suppressed by herbivores and released by herbivore removal, but this prediction may be misleading if responses are strongly contingent on plant traits and plant–plant interactions. We sought to predict responses of plant species to size-selective herbivore exclusion in an African savanna, using data on herbivore diets (from DNA metabarcoding) and plant functional traits. Our analysis had three stages. First, we identified plant traits that predicted selectivity (use relative to availability) by the dominant herbivore species excluded by different experimental treatments: megaherbivores (elephant, giraffe; ≥ 1000 kg), mesoherbivores (buffalo, zebra, impala; 40–600 kg), and dik-dik (5 kg). Several plant traits predicted selectivity across multiple herbivore species, but species’ diets were predicted by unique suites of traits. Second, we tested whether herbivore selectivity alone predicted plant responses. Elephant selectivity uniquely predicted plant responses in exclosures relative to unfenced control plots (R2 = 0.24–0.30); taxa strongly favored by elephants were ninefold more abundant inside exclosures. However, herbivore selection failed to predict differences between fenced exclusion treatments, suggesting that bottom-up effects of plant competition intensify relative to consumptive effects as large-bodied herbivores are removed. Third, including plant traits as covariates along with elephant selectivity modestly improved predictability (R2 = 0.27–0.50). Despite various sources of uncertainty and imprecision inherent to our approach, including inability to distinguish selection for different plant parts/stages, we show that elephant foraging decisions are a primary determinant of plant community dynamics. Moreover, our findings indicate that models based on readily attainable data can substantially predict plant community responses to the extirpation or reintroduction of megafauna. Future work can refine our approach by incorporating additional traits associated with plant tolerance and competition, along with more granular and mechanistic measurements of herbivore preferences and biomass consumption, to predict even more accurately how large herbivore population declines and extinctions will impact plant communities.