住家性ネズミの餌選択性を評価するための方法

抄録

A new index concerning acceptability of unpoisoned baits was worked out and applied to study the food preference of the roof rat, Rattus rattus (Linnaeus, 1758) and the Norway rat, Rattus norvegicus (Berkenhout, 1769). The index is shown as a formula, Acceptability (A)-index={(x-y)/(x+y)}×100,where x and y are the average intakes of alternative baits. Then, the formula was tested for the preferences in placement, coloration and kinds of baits. Both of these species showed the tendency to take the bait in one side more than the other side, and the average of absolute values of the A-index was as high as 22.1 in the roof rat and 17.9 in the Norway rat, respectively. Therefore, in the other choice tests, I exchanged the position of two baits daily to minimize partiality due to the influence of the food position. In the choice test on coloration of baits, there was little difference between red-colored and uncolored seeds in the intake of the roof rat (average A-index=-5.4). Although the Norway rat had a tendency to prefer red to uncolored seed (average A-index=17.8), the sample size of the A-index was only 5,and the 95% confidence limit was considerably wide. Therefore, it seemed that there was minimal effect of red coloration on the rats. In the choice test between whole rice flour and mixed powdered feed, although the roof rats showed the tendency to take one of two feed types, they entirely preferred the latter to the former (average A-index=-21.9). In conclusion, the A-index could be used as a method for estimating food preference of the commensal rat, and, moreover, it is hoped that the A-index would be used to estimate the acceptability of rodenticides in choice tests of the rats.