Résumé
Habitat connectivity influences the distribution dynamics of animals.
Connectivity can therefore shape trophic interactions, but little
empirical evidence is available, especially for large mammals. In forest
ecosystems, logging alters functional connectivity among habitat patches,
and such activities can affect the spatial game between large herbivores
and their predators. We used graph theory to evaluate how
harvesting-induced changes in habitat connectivity influence patch choice
and residency time of GPS-collared caribou (Rangifer tarandus caribou) and
moose (Alces alces) in winter in the boreal forest. We then investigated
the predator–prey game by assessing how GPS-collared wolves (Canis lupus)
adjusted their movements to changes in landscape properties and in the
networks of their prey species. We built prey habitat networks using
minimum planar graphs organized around species-specific, highly selected
habitat patches (i.e., network nodes). We found that spatial dynamics of
large herbivores were influenced not only by the intrinsic quality of
habitat patches, but also by the connectivity of those network nodes.
Caribou and moose selected nodes that were connected by a high number of
links, and moose also spent relatively more time in those nodes. By
limiting node accessibility, human disturbances influenced travel
decisions. Caribou and moose avoided nodes that were surrounded by a high
proportion of cuts and roads, but once within these nodes, moose stayed
longer than in other nodes. Caribou selectively moved among nodes with low
distance costs, and their residency time increased with distance costs
required to reach the nodes. Wolves selected their prey's nodes,
where vegetation consumed by caribou and moose was highly abundant.
Furthermore, wolves discriminated among those nodes by selecting the most
connected ones. In fact, selection by wolves was stronger for their
prey's nodes than for the prey's utilization distribution per
se, a difference that increased with the level of human disturbance.
Considering the difficulty of keeping track of highly mobile prey,
predators may benefit by targeting not only their prey's resource
patches, but also the most highly connected patches. Matrix quality and
connectivity are therefore key elements shaping the predator–prey spatial
game in human-altered landscapes because of their impact on the spatial
dynamics of the interacting species.