Abstract
Simple SummaryTwo main challenges to control invasive mammals are to maximize campaign efficacy and cost-effectiveness, and to avoid trapping other species. We designed and tested new protocols to address those challenges to control alien American mink in southern Chile. We recommend the use of the GMV-13 variant of collapsible wire cage with scent gland lure, as they are smaller, cheaper, easier to transport and effective at catching female mink and reducing the possibility of trapping native species. Trapping campaigns using GMV-13 should be conducted principally 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 female scent gland lure followed by three days with male scent gland lure. Our modelling reveals that this should result in the removal of at least 70% of the local estimated discrete mink population within the area covered by each transect.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.
Highlights
The American mink (Neovison vison) is a semi-aquatic carnivore native to North America, first introduced into Argentina and Chile in the 1930s for fur farming [1]
We spent fewer nights trapping per transect in summer but covered more transects, and this strategy provided the highest catch of mink (Figure 3a)
This is probably because mink trapping rates dropped after the 6th day, a pattern that was observed during the first campaign and was consistent over bait types (Figure 4)
Summary
The American mink (Neovison vison) is a semi-aquatic carnivore native to North America, first introduced into Argentina and Chile in the 1930s for fur farming [1]. It was introduced into Europe at the beginning of the 20th century with the same purpose [2]. In the area currently invaded by American mink in southern Chile, there are several native carnivore species, some of them of conservation concern: including the pampas cat (Leopardus colocolo); Geoffroy’s cat (Leopardus geoffroyi); kodkod (Leopardus guigna); culpeo fox (Lycalopex culpaeus); Darwin fox (Lycalopex fulvipes); gray fox (Lycalopex griseus); lesser grison (Galictis cuja); patagonian lesser weasel (Lyncodon patagonicus); southern river otter; marine otter (Lontra felina); and two subspecies of skunks (Conepatus chinga and C. chinga humboldti) [21]. Large-scale control or eradication campaigns may have unwanted casualties when trapping individuals of these species, and we need more species- and site-specific methods that provide significant conservation benefits to Patagonian wildlife [16,22]
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