Improving Trapping Efficiency for Control of American Mink (Neovison vison) in Patagonia

Abstract

Two main challenges when controlling alien American mink (Neovison vison) in Patagonia are to maximize campaign efficacy and cost-effectiveness and to avoid trapping native species. We designed and tested new variants of collapsible wire box traps, compared the efficacy of a food-based bait and a scent lure and compared catch rates in different seasons of the year. We used the data to model the efficiency rate of the trapping and to determine the trapping effort required to remove 70–90% of the estimated discrete mink population. Between January 2018 and March 2021, we operated 59 trapping transects over 103 three-day trapping periods in southern Chile. Traps were first baited with canned fish, and afterwards with mink anal gland lure. We compared the efficacy of mink capture with that of our previous study. We trapped 196 mink (125 males, 71 females), with most captures in summer. The medium-sized GMV-18 trap caught more male mink, but the more compact GMV-13 caught fewer non-target rodents and no native mammals. The scent lure was more successful than the canned fish when the previous campaign’s data were included in the analysis. There was also a significant improvement in the proportion of female mink trapped and reduced labour compared with our previous campaign that used larger traps, fish bait and 400–500 m trap spacings. We caught relatively more females than males after the third night of trapping on a transect. Our data analysis supports the use of the GMV-13 variant of wire cage trap as the best trap size: it is effective on female mink, small, cheap and easy to transport. Combined with mink anal scent lure, it reduces the possibility of trapping native species compared with other traps tested in Chile. As the most efficient method for removing at least 70% of the estimated discrete mink population within the area covered by each trap transect in southern Chile tested to date, we recommend trapping campaigns using GMV-13 during summer, with a 200-m trap spacing, for up to 6 days before moving traps to a new site, with a combination of three days with a female scent gland lure, followed by three days with a male scent gland lure.

A global review of the American mink (Neovison vison) removal techniques - Patagonia as a case study for their potential application

“…Indeed, the efficiency values of these trials are among the highest and consequently, those improvements might be applied in future large-scale management programs on the continent. The conclusions of Medina-Vogel et al (2022) agree with previous studies on trap spacing effect in mustelids (King 1980;Melero et al 2008) that showed the best capture rates, especially the concurrent capture of females and males were with traps set at 200-meter intervals Some other remarkable conclusions have been short trapping periods in each site; and the design of a smaller, cheaper and species-specific trap variant GMV-13. These studies also confirm that the use of scent gland lures increases mustelid trap efficiency (Clapperton et al 2017;Roy et al 2006) and agree with Zuberogoitia et al (2010) that trapping efforts should be focused in certain seasons of the year (Medina-Vogel et al 2022).…”

“…Many factors that increase efficiency have been highlighted in this review like the use of attractants, mainly olfactory ones, short trapping periods or increasing lineal coverage. In addition, there are some others that have been proposed previously like the new traps variant design and to concentrate culling only during certain seasons (Medina-Vogel et al 2022), the use of spatial and genetic knowledge about local mink populations (Adams et al 2014;Fraser et al 2013) or to employ sniffers dogs and techniques to flush out (as mentioned on page 44) resident mink in some stages or areas (Moore et al 2003). The selection of the most efficient techniques and protocols not only helps to achieve management proposals efficiently, but also reduces the associated costs, making control sustainable.…”

“…Los datos de las especies no objetivo se dan en número de individuos: número de especies. baits and oLfactory Lures Trap efficiency will depend on the selection of lures and trapping techniques (Medina-Vogel et al 2022). Food, mainly canned or fresh fish or chicken, has been the most common bait employed during mink trapping campaigns (Bryce et al 2011;CECPAN 2014;Davis et al 2012), although traps have been operated without any lures, especially in the United Kingdom (Craik 2008).…”

“…Even the scent of previously captured minks is considered to improve capture probability (Nordström et al 2003). There is evidence of additional advantages of using scents: capture rates of non-targets are reduced so a greater proportion of traps remain available for mink capture (Medina-Vogel et al 2022). In addition, a little quantity of scent is required, which makes transport easier.…”

Body Odours as Lures for Stoats Mustela erminea: Captive and Field Trials

“…While these odours were effective in attracting ferrets and stoats [50][51][52], synthetic lures made from the active ingredients were less attractive to stoats than to ferrets [53], and trials were discontinued. However, anal gland odours have been used successfully as trap lures to control another mustelid pest, the American mink (Neovison vison Schreber) [54][55][56]. Commercial lures containing unspecified polecat (Mustela putorius) and marten (M. foina) glandular secretions also increased the probability of detecting mustelids at camera-trap monitoring sites compared with no attractant [57].…”