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Open Access Publications from the University of California

Rodent Eradication on Cocos Island, Guam: Integrating Wildlife Damage Management, Resort Operations, and Non-Target Concerns

  • Author(s): Lujan, Dana T.
  • Vice, Daniel S.
  • Guerrero, Jesse P.
  • Candaso, Clifford C.
  • et al.

Introduced Polynesian rats threatened native bird populations and forest habitat on Cocos Island, Guam. To eliminate the threat posed by rat populations, a rodent eradication was conducted on the 33.6-hectare off-shore island in March and April 2009. An integrated approach to eradication was implemented that included trapping, bait stations, and hand broadcast of rodenticide bait. Trapping was conducted within the resort buildings, where human activity precluded the use of rodenticides. Bait stations, employed in commensal resort settings, were designed to prevent terrestrial crabs from accessing the bait. In addition, bait station deployment and retraction methods were used to reduce impacts on daily resort operations. Non-target concerns, primarily with native forest birds during broadcast operations, supported a decision to use diphacinone, a rodenticide with low avian toxicity risk. Bait consumption by the locally threatened Micronesian starling was evident during the broadcast application, but substantial monitoring for non-target impacts revealed no mortality or sublethal effects for starlings or other potential non-targets. Eradication operations on Cocos Island present a prime example of integrated wildlife damage management, combining traditional eradication methods with novel approaches to address site-specific challenges.

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