Proceedings of the Vertebrate Pest Conference

There were 1,288 sewer and 235 other utility manholes baited to control Norway rat (Rattus norvegicus) populations in downtown Boston using pulsed-baiting methods. About 15% of all sewer, 18% of phone, and 26% of electric manholes had rat activity. Sewer populations were most associated with residential areas with low flow, small diameter (<61 cm) brick sewers; in those circumstances, up to 38% of manholes had rat activity. Bait consumption in sewers (high risk areas) was 91% below baseline, five months after the fourth baiting period. Bait consumption and the number of active sewer holes were 96% and 87% below baseline, respectively, when seasonal maintenance baiting was last initiated. Reinfestation of phone/electric manholes was so minimal that maintenance baiting was not necessary or cost-effective. Subsurface baiting should be an integral part of urban rodent control programs.