Fine-scale vegetation complexity and habitat structure influence predation pressure on a declining snake

In Western Europe, omnipresent human activities have considerable impacts on habitats at several spatial scales resulting in direct shifts in habitat characteristics. These modifications in habitat features can disrupt biotic interactions such as predation. Surprisingly, although snake species are facing a worldwide decline, relationships between habitat characteristics and predation pressure in snakes remain poorly understood. The main goal of this study was to assess predation pressure on a snake species (the common adder; Vipera berus) in relation to two habitat characteristics: fine-scale (microhabitat) vegetation complexity and habitat structure (linear/non-linear). Using 2400 artificial plasticine models of adder as lures in 12 sites in Wallonia (Belgium), we quantified and compared the relative predation risk with respect to these two habitat features. We showed that, all predators combined (mammals and birds), increasing vegetation complexity had a positive impact by decreasing predation pressure, while habitat linearity increased attack risk on adders. However, for mammalian predators, increasing structural complexity reduced predation risk in non-linear habitats while this risk remained constant and substantial in linear habitats. This suggests that the abiotic benefits of linear strips or edges may be balanced by high predation risks. For bird predators, habitat linearity had no effect on attack rates while an increase in structural complexity reduced attack probabilities. In the light of these results, we suggest applying management practices that ensure a high degree of structural complexity in semi-natural habitats concerned with snake conservation. Moreover, we recommend creating non-linear, highly structured habitat elements to hamper predation pressure by mammals.

Automated summary

Human activities in Western Europe have significant impacts on habitats, affecting the characteristics of the habitat and leading to changes in predation pressure on snake species. This study focused on the common adder and found that increasing vegetation complexity reduced predation pressure, while habitat linearity increased attack risk. Mammalian predators showed reduced risk in non-linear habitats with increasing structural complexity, while bird predators had reduced attack probabilities with increased structural complexity. Management practices should prioritize high structural complexity in semi-natural habitats to conserve snake populations.