Invasive Carnivore Research Articles

Invasive carnivores in Patagonia: defining priorities for their management using the American mink (Neovison vison) as a case study

Ecologia Austral 24:183-192 (2014)Las especies exoticas invasoras amenazan la biodiversidad. Existen diferentes opciones para su manejo: prevencion, deteccion temprana, erradicacion, control, exclusion e incluso la “no accion”. A mayor complejidad de manejo, mas informacion se requiere para ejecutarlo exitosamente. Ademas, gestores e investigadores abordan la problematica con enfoques e intereses diferentes. Mientras los primeros priorizan acciones de manejo, los segundos encuentran una oportunidad para estudiar aspectos basicos y/o teoricos, no siempre aplicados al manejo. La gestion de estas especies ofrece una ocasion unica para que ambos grupos trabajen juntos en busca de beneficios mutuos. Actualmente, las decisiones de manejo suelen basarse en experiencias o informacion de otros paises, no siempre adaptables a la problematica local. En este trabajo presentamos varias experiencias de manejo en la Administracion de Parques Nacionales para exponer logros, dificultades y desafios a los que usualmente se enfrenta la gestion institucional. Encontramos que: a) ante recursos escasos es importante generar herramientas de priorizacion efectivas y redes de trabajo; b) es imprescindible involucrar a la comunidad en las acciones de manejo; c) se requieren investigaciones aplicadas al manejo especifico; y d) es necesario una detallada planificacion previa y un monitoreo de las acciones ejecutadas y de sus resultados, basados en informacion tecnica de primer nivel, ya que son aspectos claves para un manejo exitoso. Finalmente, gestores e investigadores deben cerciorarse que los resultados de estas investigaciones aplicadas sean conocidos y comprendidos por los tomadores de decisiones y la opinion publica, para asegurar el apoyo a la gestion.

Foxes are now widespread in Tasmania: DNA detection defines the distribution of this rare but invasive carnivore

Summary Invasive vertebrate species are a world‐wide threat to biodiversity and agricultural production. The presence of foxes, one of the most damaging invasive vertebrates introduced to Australia, has now been confirmed in the island state of Tasmania, placing at risk many species of native vertebrates and substantial agricultural industry. Effective eradication of such a rare but elusive carnivore requires robust strategies informed by novel but systematic detection. We combine DNA detection approaches for trace samples with systematic stratified and opportunistic surveys of carnivore scats to estimate the current distribution of foxes in Tasmania. We use that DNA evidence and other hard evidence provided by carcasses and other material to build a predictive model of fox habitat suitability for all of Tasmania. We demonstrate that this destructive species is widespread in northern and eastern Tasmania but has not yet reached the limits of its range. The widespread nature of this distribution reveals that targeting fox activity hotspots only for eradication is unlikely to be successful and that a strategic and statewide approach is required. Our habitat suitability model can provide a basis for prioritizing areas for fox management. Synthesis and applications. Our approach highlights the importance of early and pre‐emptive surveys of recently established, and therefore rare, invasive species and the necessity of providing a sound and defensible approach to determining the distribution of the invasive species. This approach provides a template for the systematic detection of rare cryptic carnivores.

Dynamics in space use of American mink (Neovison vison) in a fishpond area in Northern Germany

Telemetry of American mink Neovison vison revealed seasonal and sexual variations in home-range size, intersexual- and partially intrasexual range overlaps and spatial dynamic of territorial system. From 2003 to 2006, 14 mink (nine males and five females) were radio-tracked in a fishpond area in northern Germany. We observed comparatively large home ranges. Both sexes reduced their large summer home ranges to smaller ones in the winter period. In both seasons, male mink used significantly larger areas than female mink. During the mating season, males considerably enlarged their home ranges and roamed nearly through the entire study area. These variations and diversity of range size were discussed in connection with thermoregulatory behaviour, prey availability and distribution, population density and stability of the social system. Analysing intraspecific static interactions, we observed high intersexual overlapping rates in both the summer and winter periods. But there were no or rather very low levels of intrasexual overlapping. However, in the summer period, large home ranges of neighbouring males also overlapped to some extent, but temporal avoidance of adjacent territory holders was observed. Consequently, our results reveal intrasexual territoriality, with males having larger territories, overlapping those of females. The shifting of stable temporary home ranges observed within one season or between the same seasons of consecutive years demonstrates the highly dynamic nature of spatial behaviour among American mink. All these recorded characteristic features of spatial behaviour should be considered when planning mink control projects and measures for the management of this invasive carnivore.

Adaptation to cold and predation—shelter use by invasive raccoon dogs Nyctereutes procyonoides in Białowieża Primeval Forest (Poland)

Based on radio-tracking of raccoon dogs Nyctereutes procyonoides in Białowieża Primeval Forest (E Poland) in 1997–2002, we addressed the hypothesis that pattern of shelter use by this invasive carnivore is an adaptation to both climatic conditions and predation. Raccoon dogs used various types of shelters but were invariably concealed in dense vegetation or in the shelters created by trunks, branches, or roots of fallen trees (58% of days). Burrows (mainly badger setts) and hollow trees (mainly fallen limes) were selected on 27% and 14% of days, respectively. The pattern of shelter use varied throughout the year. In crucial periods (breeding period and winter), raccoon dogs used shelter offering better protection: burrows and hollow trees (use of which increased with decreasing ambient temperature) in winter, and hollow trees and dense vegetation during breeding and raising pups. The pattern of shelter use by raccoon dogs was also strongly modified by forest structure. Raccoon dogs living in the pristine old-growth stands (with large amounts of dead wood) utilized mainly natural shelters created by fallen trees (trunks, branches, and roots) and sedge tussocks (38% and 37%, respectively). Individuals inhabiting the managed part of the Forest used mainly burrows (43%) and thicket (23%). We recorded very strong monogamous relationships between pair mates, manifested by shared resting on 84% of days per year. We conclude that hiding behavior and plasticity in shelter use is a response to high mortality due to predation and to unfavorable climatic conditions. High adaptability to various environmental conditions may be one of the factors underlying successful range expansion of raccoon dogs in Europe.

Landscape barriers reduce gene flow in an invasive carnivore: geographical and local genetic structure of American mink in Scotland

To be effective, management programmes geared towards halting or reversing the spread of invasive species must focus on defined and defensible areas. This requires knowledge of the dispersal of non-native species targeted for control to better understand invasion and recolonisation scenarios. We investigated the genetic structure of invasive American mink (Neovison vison) in Scotland, and incorporated landscape genetic approaches to examine resultant patterns in relation to geographical features that may influence dispersal. Populations of mink sampled from 10 sites in two regions (Argyll and Northeast Scotland) show a distinct genetic structure. First, the majority of pairwise population comparisons yielded F(ST) values that were significantly greater than zero. Second, AMOVA revealed that most of the genetic variance was attributable to differences among regions. Assignment tests placed 89 or more of individuals into their sampled region. Bayesian clustering methods grouped samples into two clusters according to their region of origin. Wombling approach identified the Cairngorms Mountains as a major impediment to gene flow between the regions. Mantel pairwise correlations between genetic and geographical distances estimated as least-cost distance assuming a linear increase in the cost of movement with increasing elevation were higher than Euclidean distances or distance along waterways. Spatial autocorrelation analyses revealed stronger spatial structuring for females than for males. These results suggest that gene flow by American mink is restricted by landscape features (mountain ranges) and that eradication attempt should in the first instance break down the connectivity between management units separated by mountains.

Evidence of admixture between differentiated genetic pools at a regional scale in an invasive carnivore

Invasive species represent a major threat to biodiversity, and the understanding of their population genetics is one of the most important goals in conservation biology. Recently, it has been proposed that methods using molecular tools could help define efficient eradication strategies and should be a preliminary step in the management process. The American mink was introduced in Europe for fur farming purposes in the 1920s, and, due to escapees, several feral populations have been mentioned in the last decades. In France, feral mink have been observed since the 1970s, and the largest population, located in Brittany, is considered to be still expanding. We investigated the genetic variability and population structure of 149 feral mink and 21 farmed mink from this area using six microsatellite loci. Our results showed three genetically distinct population units at the regional scale. A pattern of isolation by distance was observed for the whole sample. In our case we explain this pattern by recent admixture of the three genetic units. Our findings suggest that populations have recently met and started to homogenise.

Invasive Indo-Pacific lionfish Pterois volitans reduce recruitment of Atlantic coral-reef fishes

The Indo-Pacific lionfish Pterois volitans, introduced to Florida waters in the early 1990s, is currently spreading rapidly throughout the Caribbean region. This invasive carnivore may cause deleterious changes in coral-reef ecosystems via predation on native fishes and invertebrates as well as competition with native predators. We conducted a controlled field experiment using a matrix of translocated coral and artificial patch reefs to examine the short-term effects of lionfish on the recruit- ment of native reef fishes in the Bahamas. Lionfish caused significant reductions in the recruitment of native fishes by an average of 79% over the 5 wk duration of the experiment. This strong effect on a key life stage of coral-reef fishes suggests that invasive lionfish are already having substantial nega- tive impacts on Atlantic coral reefs. While complete eradication of lionfish in the Atlantic is likely impossible, it would be prudent to initiate focused lionfish control efforts in strategic locations.