Slug activity density increases seed predation independently of an urban–rural gradient

Post-dispersal seed predation by slugs is increasingly being acknowledged as a potentially important contribution to this ecosystem function. However, specific drivers of predation rates in different landscape contexts are still unknown. We assessed the role of slugs as facultative seed predators along an urban–rural gradient and identified scale-dependent anthropogenic drivers that might affect either slugs or their function as seed predators. We used a combination of seed cafeterias and pitfall traps in grassy areas of eleven schoolyards and five field margins surrounded by different land-use types to assess slug activity density and seed predation rates and quantified urbanization, habitat heterogeneity and microhabitat structure. We show that slugs are important seed predators regardless of anthropogenic land use. Their activity density was a significant predictor for seed predation but increases in woody vegetation and bare soil also increased seed predation. This indicates that the magnitude of seed predation might also be affected by slug foraging activity and feeding behaviour, which might be influenced by habitat features such as the availability of vegetation and bare soil. Our results suggest that not only assessing the activity density (as proxy for relative abundance) of seed predators but also identifying effects on their feeding patterns and behaviour might increase our mechanistic understanding of relationships between land-use changes and seed predation and their impact on cultivated and wild plant species.