First results from a pilot programme for the eradication of beavers for environmental restoration in Tierra Del Fuego

CURTO, ERIO; ESCOBAR J,; SCHIAVINI, ADRIÁN; JUSIM, P

Island invasives: scaling up to meet the challenge

IUCN

Lugar: gland; Año: 2019; p. 57 - 63

A pilot project for the eradication of beavers (Castor canadensis) in Tierra del Fuego started as part of a binationalagreement, signed between Argentina and Chile, to restore the aff ected environments. The project covers ninepilot areas of diff erent landscapes and land tenures in the Argentinian part of Isla Grande de Tierra del Fuego. We report onthe results from operations in the fi rst of the pilot areas. From October 2016 to January 2017, ten trappers (named restorersfor advocacy purposes) used body-grip traps, snares and an air rifl e, in a fi rst phase, which included 2,237 trappingnights and 1,168 trap-sets. Shooting eff orts were not monitored. Traps were set for 1,401 trapping-nights and caught 175beavers at a success rate of 12.5% (captures per trap night). Snares were set for 936 snare-nights and caught 22 beaversat a success rate of 2.3%. Seven beavers were shot. Most beavers (65%) were removed during the fi rst week of trappingin the diff erent watercourse sections. Stopping trapping for a week or more did not increase effi ciency. From Marchto May 2017 restorers removed 24 survivors and/or reinvaders, including 10 from two previously untrapped colonies.Capture effi ciency for this removal period was low for body-gripping traps but not for snares. The sex ratio of catches was47% females to 53% males. The age structure of catches was 15% kits, 29% yearlings, 51% adults, with 4% not aged.An estimated total of 41 colonies was trapped, giving an average of 5.6 animals per colony. After nominal eradicationwas declared by restorers, 154 camera trapping nights were deployed to assess eradication success. Nine cameras (of 26cameras used) detected beavers. Therefore, eradication was not achieved using the methods and eff orts in the fi rst part ofthe pilot study. This highlights the need for more eff ort or the application of diff erent techniques or trapping strategies.For example, daily checking of traps may cause the animals to be cautious so, the next step in the programme will involveexploring alternative trapping methods to reduce disturbance.