Volunteers repel invading mink
9 December 2010 by Tom Marshall
Ordinary people have joined forces with scientists to wipe out invasive American mink in north-eastern Scotland and protect the native water vole they were threatening.
The marauding mustelids have menaced indigenous wildlife since they were introduced to the UK during the last century, driving out native species and unbalancing delicate river ecosystems.
Water voles have been among the biggest victims; British populations have plummeted by 96 per cent since 1950, mostly because of predation by mink.
Described in Biological Conservation, the recent success in Scotland is just the latest addition to a growing body of evidence that invasive species can be stopped and even turned back. "This project should contribute to overturning the prevailing lack of ambition about managing invasive species in Europe by providing a model for other programmes," the researchers write. "It is a strong testament to what can be achieved when empowering local communities to take a stake in their local biodiversity, and thus reason for optimism that the tide of invasion can be rolled back."
Early signs of a vole comeback are already visible, and by December 2009 some 10,000km2 of land were thought to be free of breeding mink. Trapping efforts continue, but are focused on the periphery of the target area in order to stop animals from stealthily recolonising it.
Based in the Cairngorms National Park, the project depended on tight cooperation between conservation scientists, policy-makers and stakeholders like the National Park Authority and local fisheries boards. It focused both on systematically eradicating mink and on protecting endangered water voles.
A team of University of Aberdeen biologists under Professor Xavier Lambin worked with 186 volunteers over three years. By the end of the study period, they'd removed 376 mink from a 10,570km2 area. This is the largest effort to remove invasive species ever undertaken in a mainland environment.
Part of the reason it worked was that the scientists cooperated with many other interested groups in the wider community. These ranged from gamekeepers and river bailiffs to wildlife rangers, people who manage land on behalf of big landowners and those who were simply keen to do something for the local environment.
Scientists and volunteers started off at each river's mountain headwaters, eradicating mink before gradually moving downstream. Their main weapons were specially-designed 'mink rafts' featuring a footprint-recording plate of moist clay and sand in a tunnel.
Participants returned each fortnight to check the rafts; if they saw mink footprints on the clay plate, they installed a mink trap. If they returned to find a mink, they killed it and sent details back to the scientists.
A dedicated band of volunteers looked after each river system, and the network of rafts was gradually extended downriver in what the scientists call a 'rolling carpet' strategy.
The volunteers assumed more responsibility as the project progressed - by the end of the three years, they were looking after 86 per cent of the 543 rafts deployed. They were trained to kill trapped minks humanely using powerful air guns, and relayed information on age, sex and genetics back to the researchers.
In turn, the scientists carried out statistical analysis of the data, allowing the eradication programme to adapt to changing conditions. They examined the connectedness between different areas and their mink populations to help ensure efforts were focused in the most important places.
Already, the mink eradication effort has inspired sister projects elsewhere in the country, and the various programmes may eventually be combined with the aim of creating a mink-free Scotland. In the Cairngorms, monitoring and trapping will continue for the foreseeable future, to prevent the mink from returning. To keep volunteers interested, they may be involved in other local conservation issues.
It may be possible to apply similar methods to dealing with other harmful non-native species across large areas, according to the scientists. The programme's success depended on broad public support and on the involvement of many different groups, each with different concerns but a common interest in eradicating mink.
'Turning back the tide of American mink invasion at an unprecedented scale through community participation and adaptive management'. Biological Conservation: doi:10.1016/j.biocon.2010.10.013.