Testing mechanistic explanations for mammalian predator responses to habitat edges

Abstract

Increased predator activity along habitat edges (the edge effect) is often documented in the temperate zone, but earlier studies have rarely been able to explicitly test the suggested mechanisms underlining this phenomenon. In this study, we measured the distribution of mammalian predators by scent stations and their main prey (rodents) in four types of landscape elements corresponding to an edge gradient between two habitat types; grassland and forest. We found a contrasting pattern in carnivore activities between years. Whereas carnivores did not exhibit a significant occurrence along the forest-grassland edge in the first year with low prey abundance, they were more likely to be detected along habitat edges in the subsequent year with high prey abundance. Our results do not suggest that the increased activity of carnivores at habitat edges arises as a consequence of predator overflow from higher quality habitat through the edge into lower quality habitat, but showed that most predator species focus their activity specifically to the edge structure. On the other hand, our data do not provide straightforward support for the hypothesis that predator edge preferences are caused by a spatial gradient in carnivores' main prey-rodents.

The fine-scale utilization of forest edges by mammalian mesopredators related to patch size and conservation issues in Central European farmland

“…In line with our previous results Svobodová et al 2011) and other studies (Paton 1994;Dijak and Thompson 2000;Larivière and Messier 2000), we document that the distribution of mammalian mesopredators in a fragmented landscape in Central Europe is primarily restricted to the narrow strip of forest edges. Due to the large home ranges of carnivores (Mitchell-Jones et al 1999), this pattern is likely to correspond to spatial preferences within the particular home range of each individual predator, rather than to the disproportional distribution of individual home ranges across the edge-interior gradient.…”

“…The strength of the edge effect can be closely connected to landscape type, level of habitat fragmentation, and type of habitat edge (Andrén 1995;Donovan et al 1997;Dijak and Thompson 2000;Keyser 2002;Malt and Lank 2009), and may even vary temporally (Svobodová et al 2011). The elevated activity of predators along habitat edges has been documented especially in highly and moderately fragmented landscapes (Donovan et al 1997;Lahti 2001), as well as in areas with intense agriculture or residential development (Bayne and Hobson 1997;Dijak and Thompson 2000;Keyser 2002).…”

“…Grassland habitats were entirely composed of fields for producing hay (for detailed description see Š álek et al 2009). The minimal distance between two adjoining scent stations in one transect was 50 m, which is sufficient to detect differences in carnivore fine-scale habitat utilization (Sinclair et al 2005;Šálek et al 2009;Svobodová et al 2011). In addition we analyzed the effect of habitat variables that characterize the degree of habitat fragmentation and loss at landscape scale and that may affect the distribution and landscape use of carnivores (Virgós et al 2002;Gehring and Swihart 2003;Pita et al 2009).…”

Temporal variation in nest predation risk along habitat edges between grassland and secondary forest in Central Europe

“…Nevertheless, our study indicates that predation risk between habitat edges and interiors may exhibit temporal variation. Thus, grassland-forest edges appear to be important landscape elements that contribute to trophic interactions and other ecological processes in the Central European landscape (see also Storch et al 2005;Svobodová et al 2011;Šálek et al 2010). The question thus arises, what underlies this large temporal variation in predation risk along the ecotonal interface in our study?…”

“…(2) Some predator species specifically more often use edge habitats because complementary resources from both habitat types are accessible near the edge and/or resources are concentrated along edges (ecotonal effect model, sensu Lidicker 1999; see more details on other conceptual models of the edge effect by Svobodová et al 2011).…”