Intra- and interspecific relationships of alpine ungulates reorganise along a wolf recolonisation gradient

Apex predators are recovering across many ecosystems after decades of decline, yet whether their return can restore ecological interactions disrupted by their loss remains poorly understood. Here, we used the ongoing recolonisation of grey wolves ( Canis lupus ) in the south-eastern Alps as a natural gradient of predator recovery to examine how predation risk and human disturbance shape relationships among red deer ( Cervus elaphus ), roe deer ( Capreolus capreolus ), and Alpine chamois ( Rupicapra rupicapra ). Across a gradient of time since wolf establishment, roe deer increasingly occupied sites without red deer, suggesting predator recovery alters relationships between prey species. Red deer also formed larger groups, consistent with a shift in collective behaviour under increased predation risk. Human disturbance also affected group formation in red deer and chamois. Together, these findings show that prey community structure can vary with wolf recovery, even in human-dominated landscapes, through altered associations among species and grouping within species.