Effective control of non‐native American mink by strategic trapping in a river catchment in mainland Britain

Abstract

The introduction of American mink (Neovison vison; hereafter mink) into Europe has had severe impacts on many native wildlife species, including the water vole (Arvicola amphibius) in mainland Britain. Although trapping has been widely used to attempt to control mink, managers have little direct evidence of its effect on mink density or distribution, particularly where immigration of mink from nearby areas is inevitable. Such evidence is needed to justify the use of lethal methods in conservation policy. During 2006–2010 we removed mink from the River Monnow Catchment in western Britain, using track-recording rafts to monitor continuously for mink presence, guiding a strategic trapping effort. The area monitored and trapped was increased in stages, from a core sub-catchment with 109 km of water-course in 2006, to a 421-km2 catchment with 203 km of water-course in 2009. In each successive sub-catchment, mink detection and capture rates declined rapidly to near-zero levels after trapping began. Detections and captures showed seasonal peaks in every year corresponding to known dispersal periods, but also declined steadily from year to year, with increasing periods in which we did not detect mink. These results suggested that each sub-catchment was cleared of mink within a few months, with subsequent captures attributable to immigration. On average, we detected each mink 5.1 times before capture (daily probability of detection = 0.059 per mink and raft), and trapped them 3.4 days after deploying traps in response. On average, mink entering the area were likely to have been present for less than 13 days before capture. Water voles had been extinct in the Monnow Catchment since the 1980s. During 2006–2008 (starting 6 months after mink trapping commenced), we released 700 captive-bred water voles into the treatment area to re-establish a wild population. Persistence of this population through the 4 years of the project was considered indicative of effective mink control. This study demonstrates that, even in a mainland context, a systematic trapping strategy can have a substantial impact on the density and distribution of a damaging species, in this case allowing the restoration of a native prey species. © 2013 The Wildlife Society

Compensatory immigration challenges predator control: An experimental evidence-based approach improves management

“…Our study provides support for immigration as the main compensatory demographic response of red fox to control, as in several territorial carnivores (Loveridge et al , Cooley et al , Andreasen et al , Beasley et al , Reynolds et al ). On small spatial scales (approx.…”

“…Extending the spatial scale of actions is usually proposed as a management solution to this issue (Saunders et al ). However, country‐scale management of widely distributed species, like the red fox, is typically intractable (but see Bryce et al , Reynolds et al ). In particular, our study shows that fox culling at a regional scale (i.e., 100–1,000 km 2 ) underwent similar compensation.…”

“…Indeed, there is growing empirical evidence on the crucial role of immigration from surrounding areas in compensating for local culling (hereafter compensatory immigration, Beasley et al ), especially in mammalian carnivores (Novaro et al , Loveridge et al , Cooley et al , Andreasen et al , Reynolds et al ). This spatial process may impair management actions because the geographic scale may exceed that of management areas (Bryce et al ; e.g., fox dispersal distances in Illinois: 45 km in average; range: 1–478 km; Gosselink et al ).…”

Adult sex-ratio distortion in the native European polecat is related to the expansion of the invasive American mink

“…The assumption that males are better at detecting baits appears to be unsupported by research on sex-related discrimination ability (Woodley and Baum, 2003;Berzins and Helder, 2008). However, other additional factors not addressed here may influence malebiasing in SSR in polecats and other small mustelids, as this is a general trend in all of these species, including, although to lesser extent, the American mink (Tumanov, 2003; see also Reynolds et al, 2013). Thus, it should be admitted that some possible contextual factors that might influence SSR like, for instance, season, intensity and duration of sampling effort or the use of scent attractants, were not controlled in present work.…”

Estimated mink home ranges using various home‐range estimators

“…Most estimates of mink abundance and space use have relied on harvest data and home range estimates are mostly reported as linear waterway distances (Gerell , Whitman , Stevens et al , Larivière , Haan and Halbrook ). Although several space‐use studies of American mink have been reported from Europe, where they are an exotic species (Melero et al , Zschille et al , Reynolds et al ), extrapolating results of these studies to native mink in North America is problematic because of potential differences in food resources, habitat, and cohabitating species, including European mink ( Mustela lutreola ), that may influence the behavior and activities of an exotic species (Larivière ).…”