TOXIC BAIT AVERSIONS IN DIFFERENT RAT STRAINS EXPOSED TO AN ACUTE RODENTICIDE

Because laboratory strains of rat (Rattus norwegicus) are most often u sed to develop rodenticides, it is not known whether aversions to rode nticides are developed similarly by wild and domesticated strains. Thu s, we studied and assessed the relative aversions of wild and domestic ated rats to food pellets containing the acute rodenticide zinc phosph ide under long-term, self -maintenance conditions. Our animals were ho used in cages equipped with 2 operant levers by which food pellets cou ld be obtained continuously. Over a 12-hour period, food pellets conta ining the rodenticide were available from one of the dispensers. Subse quently, untreated pellets were again made available from that dispens er. We repeated these procedures 1 week, 4 weeks, and 34 weeks later. Lever pressing rates, lever preference, and pellet consumption prefere nce indicated that wild and domesticated rats formed a long-lasting av ersion to food pellets containing zinc phosphide after only brief expo sure to a poisoned food source that usually provided a similar but har mless diet. Wild rats were superior in their ability to discriminate t he rodenticide pellets, to redirect their food-seeking behavior to a s afe source, and to retain the aversion over a long period. Our data su ggest that it would be unwise to assume that rodenticides that do not produce ''poison-shyness'' in domesticated rats will be equally succes sful on wild rats in the field.