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 (GoszczyĆski 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).