Control of Norway rats in sewer and utility systems using pulsed baiting methods

Abstract

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.