Illegal hunting represents a major threat to the conservation of predators, but its impact remains difficult to assess as there are strong incentives to conceal this criminal activity. Attributing declines of carnivores to poaching is therefore an important conservation challenge. We present a case study of the Eurasian lynx (Lynx lynx) in the Swiss Alps (Valais) where the current distribution range is smaller than in the recent past and population density is by ≥80% lower than in the adjacent Swiss Prealps. We tested four hypotheses to explain this lower density: (1) a too low density of camera-traps deployed for lynx surveys in Valais compared to the Prealps (methodological artifact); (2) less favorable environmental conditions around the camera-trap sites; (3) lower densities of the main prey; and (4) poaching. We estimated lynx and ungulate densities and environmental conditions at trail camera sites and could clearly reject the first three hypotheses because: (1) the survey protocol was similarly effective; (2) environmental conditions around the trapping sites in Valais were even more favorable for lynx detection than in the Prealps; and (3) prey supply was even larger in Valais. Concerning hypothesis 4, we discovered a network of illegal lynx traps (neck snares) in the main immigration corridor into Valais from the thriving adjacent lynx population in the Prealps, suggesting intense local poaching. Our findings substantiate the suspicions of long-lasting lynx poaching as a threat to the establishment and survival of the Valais population. The fact that instances of poaching were publicly known since 1995 but remained unabated for at least two decades, until the first conviction occurred, questions the commitment of local authorities to address this case of wildlife crime. Our study demonstrates the need for inquiries about poaching of top predators to be carried out at the highest levels of jurisdiction to avoid any risk of collusion between law enforcement agents and poachers.

The return of top carnivores to their historical range triggers conflicts with the interests of different stakeholder groups. Anticipating such conflicts is key to appropriate conservation management, which calls for reliable spatial predictions of future carnivore occurrence. Previous models have assessed general habitat suitability for wolves, but the factors driving the settlement of dispersing individuals remain ill-understood. In particular, little attention has been paid to the role of prey availability in the recolonization process. High spatial resolution and area-wide relative densities of the wolf's main ungulate prey species (red deer, roe deer and chamois) were assessed from snow-track surveys and modelled along with wolf presence data and other environmental descriptors to identify the main drivers of habitat selection of re-establishing wolves in the Western European Alps. Prey species abundance was estimated from the minimum number of individuals recorded from snow-tracks along two hundred and eighteen 1-km transects surveyed twice a year during four successive winters (2012/2013-2015/2016). Abundance estimates per transect, corrected for species-specific detection probabilities and averaged across winters, were used to model area-wide relative prey density and biomass. Confirmed wolf observations during the same four winters were used to develop a spatially explicit habitat selection model for establishing wolves, based on our estimates of prey supply and other environmental descriptors of topography, land-use and climate. Detection-corrected ungulate prey abundances and modelled relative densities varied considerably in space (0-2.8, 1.3-4.5 and 0-6.3 per 50 ha in red deer, roe deer and chamois respectively; 1.3-11.65 pooled), while total predicted prey biomass ranged from 23 to 304 kg per 50 ha. Red deer density was the most important factor explaining wolf occurrence (31% contribution), followed by roe deer density (22%), winter precipitation (19%) and presence of game reserves (16%), showing that food supply, especially red deer as the most profitable prey in the Western Alps, was the main driver of winter habitat selection during the settlement phase. Synthesis and applications. We demonstrate the crucial importance of including accurate, fine-grained information about prey supply for predicting recolonization patterns of carnivores and thus anticipating areas with potential human-wildlife conflicts where preventive measures should be prioritized.

Increasing the proportion of unmanaged forests in multi-functional forest landscapes is a primary goal of international and national conservation strategies aiming at restoring natural properties in structurally simplified forests. However, the development of structural features and associated habitat suitability for forest species is largely unknown and even controversially discussed, as the development of newly established reserves is unidirectional and passes through dense maturation stages. This may negatively affect open forest species in the first phase after reserve designation. We evaluated the effects of management cessation on key habitat characteristics of four mountain forest bird species indicative of different structural components: Capercaillie (Tetrao urogallus), Hazel grouse (Bonasa bonasia), Three-toed woodpecker (Picoides tridactylus) and Pygmy owl (Glaucidium passerinum) across four mountain regions in Central Europe. Habitat suitability was modelled based on 300 forest sites selected independently of their management status, and predicted to an independent dataset of 42 strictly protected forest reserves in the same regions. We then compared forest reserves to managed forests with species presence or absence with regard to habitat suitability and key habitat structures and related both to the time since reserve designation. For all model species, except Pygmy owl, habitat suitability in forest reserves was significantly higher than in managed forests with species' absence, but not different from managed forests with species presence. For the species associated with open forest structures (Capercaillie, Hazel grouse, Pygmy owl) habitat suitability was significantly related to the "reserve age": reserves in the first three decades after management cessation showed a significant decrease in suitability, which increased afterwards up to the maximally recorded time of 100 years. No such correlation was found for the Three-toed woodpecker associated with deadwood and barkbeetle infestations following temporally unpredictable disturbance events. Structural characteristics varied greatly in abundance and distribution, with open structures being related to the time since reserve designation. We therefore recommend focusing on mature, near-natural and structurally diverse forests when designating new strict forest reserves.