Open habitats and species differences shape space use in semi-feral cattle and horses across Danish rewilding sites

Large herbivores can strongly influence ecosystem structure and biodiversity, making knowledge of their space use important for trophic rewilding. We used GPS-tracking data collected over two years from 10 semi-feral cattle and 17 horses across ten Danish rewilding sites to analyse habitat use in a use-availability framework using resource selection functions (RSFs), complemented by direct behavioural observations. Both species showed large individual variability but overall used habitats disproportionately to availability, with higher relative use of open habitats; including dry grassland and heath-dune habitats, and lower relative use of dense shrub, conifer forest, mixed and broadleaved forest and wetlands relative to grasslands. Horses showed higher relative use of open wet and heath-dune habitats compared with cattle. Behavioural observations supported marked interspecific differences in activity budgets, with horses spending most observed time grazing and cattle allocating more time to resting and ruminating. Habitat use also varied seasonally, including increased use of wetlands and forests in summer, while supplementary winter feeding caused strong local shifts in habitat use by concentrating animal activity around winter feeding areas. These results show that habitat composition and management strongly determine where herbivore impacts are likely to be concentrated within rewilding sites, and that dense conifer-dominated stands are likely to receive relatively limited use by horses and cattle. Thus, considering herbivore space-use ecology in site planning and management and introducing herbivores with distinct digestive physiologies and foraging strategies such as horses and cattle, will improve the effectiveness of trophic rewilding.