Model description
We considered top-down and bottom-up pathways based on our predictions and on documented predator interactions in boreal ecosystems (solid lines in Figure 2, Model 1). Large carnivores (lynx and wolf) were expected to limit the dominant mesocarnivores (red fox and badger) through interference competition (Elmhagen and Rushton, 2007). Dominant mesocarnivores, red foxes, were expected to limit pine martens through the same process (Zalewska et al., 2021). We considered that bottom-up factors (proportion of agricultural land and EVI) would affect all species, but expected different strength for different seasons, with bottom-up factors having a stronger effect than top-down factors in winter than in summer (Elmhagen and Rushton, 2007, Stoessel et al., 2018). We anticipated that large carnivores would not interfere with each other, since their interactions appear to be negligible (Wikenros et al., 2012, Schmidt et al., 2009). Humans were expected to limit large carnivores through disturbance and culling (Dorresteijn et al., 2015), and to have a positive effect on dominant mesocarnivores due to food subsidization (Gompper and Vanak, 2008).
Additionally, we proposed three other alternative models to test against Model 1. This is because there is a large potential for intraguild competition between badger and the other two mesocarnivores (red fox and pine marten). The three of them can occupy similar ecological niches, share the same den sites (Macdonald et al., 2004, Mori et al., 2015) and, being opportunistic generalists, may share foods such as earthworms, smaller vertebrates, eggs and fruits (Macdonald, 1980, Kauhala et al., 1998, Torretta et al., 2016, Prigioni et al., 2008). However, differential use of time and space may enable coexistence (Zalewska et al., 2021). Therefore, we added an additional pathway from badger to red fox (Model 2 in Figure 2) and then a second pathway from badger to pine marten (Model 3 in Figure 2). Moreover, pine martens are considered to avoid urban areas (GoszczyƄski et al., 2007, Fusillo et al., 2009), although recent research suggest that they can adapt to live in areas with anthropogenic disturbances (Weber et al., 2018). Therefore, we added a third pathway from humans to pine marten (Model 4 in Figure 2).