Genetic tagging reveals a significant impact of poison baiting on an invasive species

Globally, invasive predators are major pests of agriculture and biodiversity and are the focus of comprehensive control programs. Because these species are typically elusive, wary of traps, and occur at low densities, their fundamental population dynamics are difficult to determine and quantitative evaluations of control programs are rarely conducted. Noninvasive DNA analysis has the potential to resolve this long‐standing limitation to pest management. We carried out a landscape‐scale experiment to quantify reduction in the abundance of a red fox ( Vulpes vulpes ) population when baited with sodium fluoroacetate (1080) poison (the most widely used method of fox control in Australia). We collected fox hairs with hair snares during 4 4‐day sessions over the course of 6 months at a site in semi‐arid Western Australia. The first session took place in late summer just prior to when juvenile foxes typically disperse, and the final session followed aerial baiting with 1080 poison. We obtained consensus microsatellite genotypes from 196 samples, and used them to conduct both spatially explicit and open model capture–recapture analysis. Twenty‐eight percent of trap nights yielded hair samples suitable for identification of individual foxes, which is more than an order of magnitude greater than trapping rates reported with conventional techniques. Fox density changed little during 3 pre‐baiting sessions and averaged 0.73 foxes/km 2 (±0.33 SE), which is less than most previous trap‐based estimates for Australian foxes. Density dropped significantly in response to baiting to 0.004 foxes/km 2 . Prior to baiting, the apparent survival of foxes remained static (0.72 ± 0.14 SE), but in response to baiting it dropped precipitously and was effectively zero. This experiment provides the first quantitative assessment of the effectiveness of 1080 poison baiting for reducing fox density, and in this case demonstrates it to be a highly effective method for culling foxes from a region. Further, it demonstrates that noninvasive DNA analysis will provide significantly more data than conventional trapping methods. This method is likely to provide greater precision and accuracy than conventional methods and therefore result in more robust evaluations of management strategies for the fox in Australia, and for cryptic species elsewhere. © 2011 The Wildlife Society.