Cost‐distance analysis of mesopredators as a tool for avian habitat restoration on a naturally fragmented landscape

Abstract

Removal of mammalian mesopredators is a strategy frequently applied to problems of conservation management, such as protection of rare or endangered species. Effectiveness of predator removal is often dependent on the ease with which additional predators can immigrate into the removal area. We applied cost-distance analysis, coupled to a sensitivity analysis, and least-cost path analysis to raccoons (Procyon lotor) and red foxes (Vulpes vulpes) on the Virginia barrier islands to determine the landscape resistance (i.e., difficulty) for mesopredators to reach individual islands from both mainland and island sources, to assess the relative role of mainland versus island populations as sources of immigrants to unoccupied (or depopulated) islands, and to formulate strategies that focus management efforts on a few key predator sources. The minimum energetic resistances to immigration varied over 3 orders of magnitude, making some islands better targets for removal efforts than others. Additionally, because of differences in the distribution of resident populations on the islands, resistance to immigration to a typical island is at least 3 times less for raccoons than for red foxes. Landscape resistance to red fox immigration is typically lower from the mainland, whereas for raccoons inter-island movements are typically less costly. Empirical data from long-term field studies of raccoons and red foxes in this system support the resistance structure identified. Overwater transits made by marked and resighted raccoons all were relatively short and relatively low-cost. Similarly, islands that were recolonized following the removal of raccoons and red foxes all were characterized by very low resistance values. These results are used to identify specific islands for which predator removal efforts are most likely to be successful in aiding the recovery of beach-nesting and colonial waterbirds in this system. A similar approach may be applied in any landscape where there are distinct differences in the costs of traversing different elements of the landscape. Ó 2015 The Wildlife Society.

Biases and information gaps in the study of habitat connectivity in the Carnivora in the Americas

“…This approach can be adopted in regions where large carnivorans are increasingly scarce (e.g. El Salvador, Uruguay), and where meso‐carnivore species have taken on the role of top predators (Roemer et al 2009, Porter et al 2015, Bou et al 2019).…”

Direct and Indirect Interactions between Landscape Structure and Invasive or Overabundant Species

“…For instance, Porter et al [102] used landscape resistance to identify specific islands where removal of mammalian mesopredators (raccoons, Procyon lotor and red fox, Vulpes vulpes) efforts would be most successful. Their data showed that islands recolonized after the removal of raccoons and red foxes had very low resistance values (i.e., energetically easier for the mammals to reach them).…”

Alligator presence influences colony site selection of long-legged wading birds through large scale facilitative nest protector relationship

“…In addition to wading birds potentially isolating themselves from the mainland and from landmasses that could host raccoons, we thought wading birds might also seek out islands that are more isolated from other colonies when alligator presence is unlikely. We predicted that islands farther from other wading bird colonies would be less enticing to raccoons, who will readily travel between close colony islands 87 . We measured the shortest distance from the focal colony to the next nearest wading bird colony.…”