Habitat use of rewilded horses and cattle as related to the functional and structural composition of plant communities in a European restored wetland ecosystem

Rewilding initiatives in European open and semi-open lowlands increasingly involve cattle and horses for ecological restoration, especially in wetland areas of high conservation value. These large herbivores contribute to spatial heterogeneity and enhance biodiversity by shaping ecosystems through movement, grazing, and resting behaviours. However, the effect of their site-specific habitat use patterns on plant communities remains unclear. In this study, we investigated the fine-scale spatiotemporal distribution of rewilded cattle and horses in a recently restored alluvial grassland in a French nature reserve. We explored differences in habitat use between the two species during summer and winter on a macrohabitat scale and examined structural and functional changes in vegetation traits over four years, focusing on plant height, patch cover, species richness, and light preference, nutrient-tolerance, and mowing/grazing tolerance of plants. The study site, a former agricultural area converted into a restored alluvial nature conservation site, allowed observation of ecological processes from a "zero state". Our results suggest that cattle and horses exhibit similar habitat use with seasonal variations, potentially indicating partially shared feeding niches. The mixed-species grazing prevented vegetation overgrowth by keeping plant cover and vegetation height under control, yet without causing destructive impacts. The two herbivore species induced a clear increase in grazing-tolerant plants and slight changes in the abundance of light-preferring and nutrient-tolerant species. Synthesis: Overall, we found that the varying spatiotemporal distribution of rewilded horses and cattle likely induces changes in plant community on the patch scale but results in vegetation stability on the landscape scale, which is known to facilitate ecosystem functioning. Our study therefore informs managers of conservation initiatives, proposing rewilding with year-round grazing horses and cattle a promising strategy for ecological restoration and natural habitat maintenance in wetland areas.