Consumption and efficacy of rodent baits to Norway rats

Abstract

A method currently being used by the Department of Conservation to prevent reinvasion of rodent-free offshore islands aims to increase the stability and life of toxic bait by wrapping it in tinfoil or placing it into plastic ziplock bags. A laboratory study was conducted to assess the acceptance of the baits presented in this manner. Wild Norway rats (Rattus norvegicus) were used to assess the consumption of Storm® wax blocks, Talon® 50WB wax blocks, Talon® 50WB wrapped in tinfoil, or Talon® 50WB placed in a plastic ziplock bag. Each rat was offered a choice of toxic bait and non-toxic RS5 pellet baits as a control over four nights. All test baits had low consumption, resulting in very low mortality. When bait was wrapped in tinfoil or placed in a ziplock plastic bag, its consumption was reduced even further, resulting in no deaths within these treatment groups. These baits and the way they are currently being used appear to be unsuitable for control of Norway rats on offshore islands.