Predation by pine martens (Martes martes) and red foxes (Vulpes vulpes) is an important factor influencing the population dynamics of capercaillie grouse (Tetrao urogallus). However, there is a knowledge gap regarding the relative effects of these mesopredators on the reproductive success of capercaillie. To better understand how various landscape factors influence nest predation by pine martens and red foxes, we monitored capercaillie nests in Norway between 2009 and 2014 using camera trap. We classified the fate of 156 nests and employed a cause-specific hazard model to evaluate the competing risks of capercaillie nest predation, while accounting for landscape covariates such as distance from nest to forest-clearcut edges, proximity to roads, and agricultural land density. We found that predation by pine martens and red foxes was the predominant hazard to capercaillie nests, with similar daily predation rates observed for both mesopredators. Nest predation by pine martens decreased with increasing agricultural land density and tended to increase along gradients from clearcuts to forest interiors. Moreover, pine marten predation tended to decrease with increasing distance from roads. Nest predation by red foxes increased with distance from roads, but only in areas characterized by high density of agricultural land. Red fox predation was not associated with distance to forest-clearcut edges or to agricultural land density. Our findings show that landscape factors differentially influence pine marten and red fox predation on capercaillie nests and highlight the importance of considering predator-specific effects while managing populations of game birds and their predators.

Interactions among coexisting mesocarnivores can be influenced by different factors such as the presence of large carnivores, land-use, environmental productivity, or human disturbance. Disentangling the relative importance of bottom-up and top-down processes can be challenging, but it is important for biodiversity conservation and wildlife management. The aim of this study was to assess how the interactions among mesocarnivores (red fox Vulpes vulpes, badger Meles meles, and pine marten Martes martes) are affected by large carnivores (Eurasian lynx Lynx lynx and wolf Canis lupus), land cover variables (proportion of agricultural land and primary productivity), and human disturbance, as well as how these top-down and bottom-up mechanisms are influenced by season. We analyzed three years (2018-2020) of camera trapping data from Norway and used structural equation models to assess hypothesized networks of causal relationships. Our results show that land cover variables are stronger predictors of mesocarnivore activity than large carnivores in Norway. This might be caused by a combination of low density of large carnivores in an unproductive ecosystem with strong seasonality. Additionally, all mesocarnivores showed positive interactions among each other, which were stronger in winter. The prevalence of positive interactions among predators might indicate a tendency to use the same areas and resources combined with weak interference competition. Alternatively, it might indicate some kind of facilitative relationship among species. Human disturbance had contrasting effects for different species, benefiting the larger mesocarnivores (red fox and badger) probably through food subsidization, but negatively affecting apex predators (wolf and lynx) and smaller mesocarnivores (pine marten). In a human-dominated world, this highlights the importance of including anthropogenic influences in the study of species interactions.