Data from: Prey selection of Scandinavian wolves: single large or several small?

Research on large predator-prey interactions are often limited to the
predators’ primary prey, with the potential for prey switching in systems
with multiple ungulate species rarely investigated. We evaluated wolf
(Canis lupus) prey selection at two different spatial scales, i.e., inter-
and intra-territorial, using data from 409 ungulate wolf-kills in an
expanding wolf population in Scandinavia. This expansion includes a change
from a one-prey into a two-prey system with variable densities of one
large-sized ungulate; moose (Alces alces) and one small-sized ungulate;
roe deer (Capreolus capreolus). Among wolf territories, the proportion of
roe deer in wolf kills was related to both pack size and roe deer density,
but not to moose density. Pairs of wolves killed a higher proportion of
roe deer than did packs, and wolves switched to kill more roe deer as
their density increased above a 1:1 ratio in relation to the availability
of the two species. At the intra-territorial level, wolves again responded
to changes in roe deer density in their prey selection whereas we found no
effect of snow depth, time during winter, or other predator-related
factors on the wolves’ choice to kill moose or roe deer. Moose population
density was only weakly related to intra-territorial prey selection. Our
results show that the functional response of wolves on moose, the species
hitherto considered as the main prey, was strongly dependent on the
density of a smaller, alternative, ungulate prey. The impact of wolf
predation on the prey species community is therefore likely to change with
the composition of the multi-prey species community along with the
geographical expansion of the wolf population.