Studies on food selection behaviour of the Norway rat (Rattus norvegicus) on farms

Measures used to control Norway rats (Rattus norvegicus Berk.) on farms are frequently unsuccessful due to poor bait uptake. In pest-control operations, rats always have the choice between the farm's own food resources and the bait. In this study we analysed the individual selection behaviour in two rat colonies when the rats were offered a familiar bait which matched the food on the farm and a bait which was unknown. Bait stations equipped with video and transponder technology were installed in two differently structured areas on a farm. In four experiments, a familiar foodstuff (rolled oats) was put out for 3 days, and then at one of the stations, a test bait was put out for 4 days. The relative palatability of the test baits was known from laboratory experiments. The visits of marked individuals were registered, and the amounts consumed were estimated in the video evaluation. Location preference was determined by offering identical food in two neighbouring bait stations. Social interaction was evaluated using the video recordings. The bait stations were visited on a daily basis irrespective of the supply. Food selection patterns (and bait acceptance) observed in the two differently structured areas on the farm were different. However, the relative palatability among the four test baits was stable and agreed with the ranking in laboratory experiments. Over the days of the experiment there was no significant difference in bait acceptance. Location preference and social interaction influenced the choice of bait station. The results show that it is possible to predict bait palatability in the laboratory, which is an important prerequisite for good bait uptake. However, the bait acceptance level is ultimately determined by the prevailing living conditions in the respective area. For optimising bait uptake, the structure of the areas on the farm must be considered just as much as findings about location preferences and social interaction. © Springer-Verlag 2005.