Efficacy of anticoagulant-free alternative bait products against house mice (Mus musculus) and brown rats (Rattus norvegicus).

The attractiveness and efficacy of four anonymous anticoagulant-free alternative rodenticides (active ingredients cellulose or plaster) were tested on wild strain groups of house mice (Mus musculus Linnaeus) and brown rats (Rattus norvegicus Berkenhout) in laboratory choice and no-choice experiments. In no-choice tests, the rodenticide product was offered ad libitum to the animals for 21 days (mice) and 10 days (rats), respectively. In choice tests, the rodenticide product and non-poisoned food were offered for 28 days (mice) and 14 days (rats). Two products with cellulose (C1 and C2) as the active ingredient were tested against both mice and rats. In two no-choice tests with mice, all animals died within 14 days (C1) and 21 days (C2); in a third no-choice test, 11% (2/18) of mice survived (C1: 21 days). In all three tests, numerous incidents of cannibalism were observed. The attractiveness of cellulose baits was tested for one product (C1) in three trials against normal food pellets. In all trials, bait consumption was low and all mice survived (15-34 days). Two no-choice trials with cellulose baits (C1) were conducted on groups of Rattus norvegicus; 11 of 12 rats survived the bait feeding period and no cannibalism or sign of aggression between conspecifics was observed. Two plaster-based (CaSO4 0.5H2O) products (P1 and P2) were tested against both mice and rats; in no-choice tests, only one mouse (n= 20) and no rats (n= 8) were killed, although the baits proved to be attractive for rats and mice in choice tests. The results of these experiments suggest that neither cellulose-based nor plaster-based rodenticides are suitable agents for the control of Mus musculus and Rattus norvegicus.