Melero Y., Cornulier T., Oliver M.K., Lambin X. (2018) Ecological traps for large-scale invasive species control: Predicting settling rules by recolonising American mink post-culling. Journal of Applied Ecology. 55: 1769-1779.EnlaceDoi: 10.1111/1365-2664.13115
Management programmes seeking to reduce the density of invasive species must overcome compensatory processes, such as recolonisation by dispersers from non- or partially controlled areas. However, the scale and drivers of dispersal in such contexts are poorly known. We investigated the dispersal patterns of American mink re-invading 20,000 km2 of their non-native range during a culling programme led by citizen conservationists. Using multinomial models, we estimated the contributions of density dependence, proxies for patch quality and distance from the natal patch on mink settlement. Seventy-seven per cent of mink dispersed and settled in non-natal patches. Dispersal distances were large with settlement probabilities only reduced by half at c. 60 km, and 20% of mink dispersing >80 km. Females were more attracted to high-quality patches, mostly found at low altitudes. Males favoured patches with intermediate current densities and consistently high quality. Synthesis and applications. We predicted post-culling recolonisation by a non-native mobile carnivore over a large spatial scale by using information on relative densities obtained during management interventions, largely carried out by citizen conservationists. This was possible through continued monitoring of the area designed to feed into the adaptive management process of the control project. High mink mobility dictates management should take place on very large spatial scales to minimise re-invasion from uncontrolled areas. Our research shows both males and females are attracted to patches with previously consistent occupation, which provides a degree of predictability to patterns of recolonisation. Targeting control to patches that are attractive to immigrant mink requires knowledge of current mink density. Creating so-called ecological traps in the face of ongoing immigration from peripheral areas provides a promising tool to effectively control mobile invasive species. © 2018 The Authors. Journal of Applied Ecology © 2018 British Ecological Society
Melero Y., Stefanescu C., Pino J. (2016) General declines in Mediterranean butterflies over the last two decades are modulated by species traits. Biological Conservation. 201: 336-342.EnlaceDoi: 10.1016/j.biocon.2016.07.029
Species' responses to environmental changes are highly idiosyncratic and context-dependent. Although intrinsic traits (i.e. those that define species niches) may play a key role, little empirical evidence exists regarding their relationship to demographic responses. We used data for 66 butterfly species representing five ecological and two life-history traits to study the effect these factors have on population growth rates and variations in populations. Using a novel methodological approach, we provide here improved estimates of population change. Our results reveal declines in 70% and increases in 23% of the studied species, clear evidence of more serious population declines in Catalan butterflies than those that have previously been reported. Declines were associated with species' degree of habitat specialisation and the number of generations. For all species, fluctuations were greater within than between years and, on average, the latter was 1.5 times greater. Our results indicated that habitat specialists and multivoltine species are more likely to suffer severe annual fluctuations in population abundance; and that multivoltine species and extreme larval specialists had the most marked fluctuations within seasons. We also found higher resilience to environmental changes in generalist species, which is concordant with biotic homogenisation in disturbed communities. However, among the declining species there were also many generalists, which indicates a potential general reduction in this group that goes beyond faunal homogenisation. Given butterflies are biodiversity indicators, these patterns are a possible reflection of an overall impoverishment in biodiversity. © 2016 Elsevier Ltd
Oliver M.K., Piertney S.B., Zalewski A., Melero Y., Lambin X. (2016) The compensatory potential of increased immigration following intensive American mink population control is diluted by male-biased dispersal. Biological Invasions. : 1-15.EnlaceDoi: 10.1007/s10530-016-1199-x
Attempts to mitigate the impact of invasive species on native ecosystems increasingly target large land masses where control, rather than eradication, is the management objective. Depressing numbers of invasive species to a level where their impact on native biodiversity is tolerable requires overcoming the impact of compensatory immigration from non-controlled portions of the landscape. Because of the expected scale-dependency of dispersal, the overall size of invasive species management areas relative to the dispersal ability of the controlled species will determine the size of any effectively conserved core area unaffected by immigration from surrounding areas. However, when dispersal is male-biased, as in many mammalian invasive carnivores, males may be overrepresented amongst immigrants, reducing the potential growth rate of invasive species populations in re-invaded areas. Using data collected from a project that gradually imposed spatially comprehensive control on invasive American mink (Neovison vison) over a 10,000 km2 area of NE Scotland, we show that mink captures were reduced to almost zero in 3 years, whilst there was a threefold increase in the proportion of male immigrants. Dispersal was often long distance and linking adjacent river catchments, asymptoting at 38 and 31 km for males and females respectively. Breeding and dispersal were spatially heterogeneous, with 40 % of river sections accounting for most captures of juvenile (85 %), adult female (65 %) and immigrant (57 %) mink. Concentrating control effort on such areas, so as to turn them into “attractive dispersal sinks” could make a disproportionate contribution to the management of recurrent re-invasion of mainland invasive species management areas. © 2016 The Author(s)
Ruiz-Suárez N., Melero Y., Giela A., Henríquez-Hernández L.A., Sharp E., Boada L.D., Taylor M.J., Camacho M., Lambin X., Luzardo O.P., Hartley G. (2016) Rate of exposure of a sentinel species, invasive American mink (Neovison vison) in Scotland, to anticoagulant rodenticides. Science of the Total Environment. : 0-0.EnlaceDoi: 10.1016/j.scitotenv.2016.06.109
Anticoagulant rodenticides (ARs) are highly toxic compounds that are exclusively used for the control of rodent pests. Despite their defined use, they are nonetheless found in a large number of non-target species indicating widespread penetration of wildlife. Attempts to quantify the scale of problem are complicated by non-random sampling of individuals tested for AR contamination. The American mink (Neovison vison) is a wide ranging, non-native, generalist predator that is subject to wide scale control efforts in the UK. Exposure to eight ARs was determined in 99 mink trapped in NE Scotland, most of which were of known age. A high percentage (79%) of the animals had detectable residues of at least one AR, and more than 50% of the positive animals had two or more ARs. The most frequently detected compound was bromadiolone (75% of all animals tested), followed by difenacoum (53% of all mink), coumatetralyl (22%) and brodifacoum (9%). The probability of mink exposure to ARs increased by 4.5% per month of life, and was 1.7 times higher for mink caught in areas with a high, as opposed to a low, density of farms. The number of AR compounds acquired also increased with age and with farm density. No evidence was found for sexual differences in the concentration and number of ARs. The wide niche and dietary overlap of mink with several native carnivore species, and the fact that American mink are culled for conservation throughout Europe, suggest that this species may act as a sentinel species, and the application of these data to other native carnivores is discussed. © 2016 The Authors.
Melero Y., Robinson E., Lambin X. (2015) Density- and age-dependent reproduction partially compensates culling efforts of invasive non-native American mink. Biological Invasions. 17: 2645-2657.EnlaceDoi: 10.1007/s10530-015-0902-7
Management strategies of wildlife species must pay due regard to density dependent changes in vital rates. Knowledge of density dependent relationships is sparse for most species but such knowledge ought to inform adaptive management. Using data from a large-scale, 6 years of control effort of the invasive non-native American mink (Neovison vison) in Scotland, we analysed density dependent changes in reproduction as revealed by placental scar counts in culled females. Control strongly reduced mink density but it varied substantially over time and space, reflecting variation in when control was initiated in each river section. We used hurdle statistical models to simultaneously relate the probability of conception, litter size and female age to prevailing mink density in river sections where the female was culled. Both the probability of conceiving a litter (average 0.81) and litter size (average 5.52 pups) increased as the density of females, but not males, declined. In addition, there was a senescent decline in both components of fecundity, which given culling of mink and subsequent reinvasions, resulted in a younger population, adding further to density dependent compensation in fecundity. There was no evidence of depensation, even at the lowest density. The predicted combined impact of changes in density and age structure could lead to an increase in fecundity of up to 2.1 pups per female occupying or reinvading the controlled area. Control strategies must be sufficiently adaptable and robust in order to overcome this compensation and suppress densities of mink and other invasive mammals. © 2015, Springer International Publishing Switzerland.
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