U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

Fall 2019


U.S. Government Work


Human–Wildlife Interactions 13(2):226–237, Fall 2019 • digitalcommons.usu.edu/hwi


Commensal rodents (invasive rats, Rattus spp.; house mice, Mus musculus) are well established globally. They threaten human health by disease transfer and impact economies by causing agricultural damage. On island landscapes, they are frequent predators of native species and affect biodiversity. To provide managers with better information regarding methods to suppress commensal rodent populations in remote island forests, in 2016 we evaluated the effectiveness of continuous rat trapping using snap-traps, Goodnature® A24 self-resetting rat traps, and a 1-time (2-application) hand-broadcast of anticoagulant rodenticide bait pellets (Diphacinone-50) applied at 13.8 kg/ha per application in a 5-ha forest on Oahu, Hawaii, USA. We compared rat and mouse abundance at the rat trapping site to a reference site by monitoring rodent tracking tunnels, which are baited ink cards in tunnels that allow footprints of animal visitors to be identified. We found that trapping reduced rat, but not mouse, abundance. The rodenticide treatment did not further reduce rat populations (P = 0.139), but temporarily reduced the mouse populations (P < 0.001; from 33% tracking to 0% for 1.3 months). Our study highlighted the role of continuous trapping for rats and rodenticide baiting for mice as effective methods to suppress commensal rodent populations in remote island forests to protect native species biodiversity.