Smarter baits: The effects of stress on bait aversion and options to avoid the development of bait aversions

In poisoning operations, sublethal consumption of the toxin, can produce bait aversion. This decreases the effect of the poisoning and may create problems due to the presence of uneaten toxin in the environment. The use of new bait additives may prevent aversion development. Here I report the effects of two bait additives, corticosterone and mifepristone, in altering bait aversion development in rats exposed to the widely used poison, monofluoroacetate (1080). Corticosterone is a glucocorticoid hormone, released in response to stress. Mifepristone (Ru 38486), inhibits the actions of this hormone. Imposed stress as well as administration of corticosterone, decreased consumption. Concurrent administration of mifepristone prevented these decreases. Mifepristone in low doses increased aversion in stressed, but not unstressed rats. At high doses, mifepristone both increased consumption and decreased aversion in all rats following exposure to 1080. Administration of corticosterone also produced dose-dependent effects on aversion. At low doses in unstressed rats corticosterone, alone, increased aversion, while at high doses in all rats it decreased aversion. Stress, and the hormonal outcome of this state, may thus contribute to aversion by influencing both consumption and aversion development.