BEHAVIOR AND ACTIVITY OF COMMENSAL ROOF RATS AROUND BAIT STATIONS AND TRACKING TUNNELS IN SOUTHERN CALIFORNIA: INSIGHTS TO IMPROVE MANAGEMENT

Invasive rats (Rattus sp.) are globally distributed and cause significant harm to both humans and the environment. They are often controlled with rodenticides in bait stations, however, rat behavior around bait stations is not well understood. I conducted a series of field assessments in Orange County, California, USA, to understand the behavior of roof rats (R. rattus) around rodenticide bait stations and determine whether tracking tunnels could provide indices of rat activity and abundance prior to management. The first assessment consisted of three separate trials and used digital game cameras to determine whether different bait stations or baiting approaches influence station visitation by rats. Bait station design had little effect on use of stations by rats, but the presence of supplemental bait increased the risk of station entry and the likelihood of bait removal. The second assessment compared relative abundance and activity estimates of rats using tracking tunnels to estimates derived from cameras, snap traps, and live traps. Tracking tunnel indices were positively associated with activity and abundance estimates from cameras and live traps. Lastly, I conducted a pilot test of a passive integrated transponder (PIT) tag reader for detecting visits to stations by individually-tagged rats. The reader detected most entrances into the bait station (71%), but reading accuracy should be improved to ensure all tagged individuals can be reliably detected. My results fill some of the existing knowledge gaps related to the behavior of commensal rats around management devices and improve our ability to control rodent pests.