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Conner, L.M.; Morris, G.
Impacts of Mesopredator Control on Conservation of Mesopredators and Their Prey
2015  PLoS ONE (10): e0137169

Declining large carnivore populations, increased habitat fragmentation, declining interests in fur trapping, and other anthropogenic factors can all lead to increased mesopredator populations and these may negatively impact biodiversity. Lethal mesopredator control potentially mitigates some of these effects but can be controversial, largely because impacts on mesopredator populations have not been evaluated. Estimating these impacts may reduce controversies while increasing our understanding of when lethal control may be beneficial. Therefore, we analyzed published mesopredator removal data to determine if mesopredator removal rates changed over time. Removals of medium,(e.g., raccoons (_Procyon lotor_) or red foxes (_Vulpes vulpes_), and large, i.e., bobcats (_Lynx rufus_) or coyotes (_Canis latrans_), mesopredators were consistent from year to year and over the duration of study (i.e., number removed during the first and last years of studies were similar). In contrast, removals of small mesopredators, e.g., weasels (_Mustela_ spp.) or spotted skunks (_Spilogale putorius_), declined over the duration of study. Study area size, number of species targeted for removal, and duration of removal effort were poor predictors of removal rates. Our analyses suggest that: (1) control, as typically implemented, is unlikely to cause negative long-term impacts on populations of medium and large mesopredators but may negatively impact small mesopredators, (2) if mesopredator control benefits prey, recurring removals will generally be needed to maintain benefits, and (3) timing of removals will be important to achieve management goals. We suggest that mesopredator control efforts are frequently spatially structured harvests from continuously distributed populations. This may explain (1) why removal of small mesopredators declined over time; whereas, medium and large mesopredator removals remained consistent, and (2) why some prey failed to respond to mesopredator control efforts.

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