Understanding changes over time in the distribution of interacting native and invasive species that may be symptomatic of competitive exclusion is critical to identify the need for and effectiveness of management interventions. Occupancy models greatly increase the robustness of inference that can be made from presence/absence data when species are imperfectly detected, and recent novel developments allow for the quantification of the strength of interaction between pairs of species.
We used a two-species multi-season occupancy model to quantify the impact of the invasive American mink on the native European mink in Spain through the analysis of their co-occurrence pattern over twelve years (2000-2011) in the entire Spanish range of European mink distribution, where both species were detected by live trapping but American mink were culled. We detected a negative temporal trend in the rate of occupancy of European mink and a simultaneous positive trend in the occupancy of American mink. The species co-occurred less often than expected and the native mink was more likely to become extinct from sites occupied by the invasive species. Removal of American mink resulted in a high probability of local extinction where it co-occurred with the endemic mink, but the overall increase in the probability of occupancy over the last decade indicates that the ongoing management is failing to halt its spread. More intensive culling effort where both species co-exist as well as in adjacent areas where the invasive American mink is found at high densities is required in order to stop the decline of European mink. (C) 2014 Elsevier Ltd. All rights reserved.
G.S. was supported by a FPU fellowship grated by the Spanish Ministry of Education, Culture and Sports (AP2008-01894). This study was supported by European LIFE programs, the Spanish Environment Department, Tragsatec, Álava Regional Government (LIFE 00/NAT/E/7335), La Rioja Regional Government (LIFE 00/NAT/E/7331), Castilla and León Government (LIFE 00/NAT/E/7299) and the Regional Governments of Aragón, Bizkaia, Burgos, Cantabria, Gipúzkoa, Navarra, Soria and Zaragoza. We thank all technicians and forest rangers of the administrations listed above and all the people that have participated in the trapping sessions and/or have contributed with original data. We wish to thank Christopher Sutherland for the help in improving our work and Asún Gómez and Madis Podra for the useful comments and the contribution in collecting and providing the original data.
- Competitive exclusion
- Invasive species
- Mustela lutreola
- Neovison vison
- Two-species multi-season occupancy model
- species borders
- gene flow