A leap in scale for invasive species management: a medium‐scale beaver eradication pilot project

Abstract

In 1946, 20 beavers (Castor canadensis) were introduced inTierra del Fuego, Argentina, and over the last 70 years, thepopulation has expanded, severely affecting riparian environments.In 2008, Argentina and Chile agreed to restore theenvironments affected by beavers through their eradication.The objectives of this paper were to assess the trapping effortand cost required to remove beavers, and to determinethe factors that influence capture success. The study wasconducted over 7 pilot areas in the Argentine part of Tierradel Fuego. Ten trappers using body‐grip traps, snares, andshooting carried out an eradication pilot project betweenOctober 2015 and June 2018. Trappers acted in 505 colonies,performing 9,751 trapping episodes, and capturing 1,012beavers. In the mountain range zone, trappers needed onaverage 23 trapping episodes/km of watercourse. Capturesuccess was best explained by trap placement and trap type.We estimated a required investment of 31 million US dollarsover 17 years for a full beaver eradication in the Argentinepart of Tierra del Fuego. We concluded that by using mainlybody‐grip traps, eradication is feasible and it allows trappingin neighboring colonies simultaneously, without the need tocheck traps daily. Traps should be set preferably on dams,dams should be broken only after the first captures, andtrappers should be trained to capture all individuals.