Deer density drives habitat use of establishing wolves in the Western European Alps

1. 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. 2.
High-spatial-resolution, 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. 3. Prey
species abundance was estimated from the minimum number of individuals
recorded from snow-tracks along 218 1km transects surveyed twice a year
during four successive winters (2012/13–2015/16). 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. 4. 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. 5.
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 50ha
in red deer, roe deer and chamois, respectively; 1.3–11.65 pooled), while
total predicted prey biomass ranged from 23–304kg per 50ha. 6. 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.
7. 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.