Ortho-aminoacetophenone, a non-lethal repellent : the effect of volatile cues vs. direct contact on avoidance behavior by rodents and birds

Taxonomic differences in responsiveness to chemosensory irritants are prevalent among avian and mammalian species and represent a major obstacle to the development of general vertebrate repellents. We evaluated the effect of ortho-aminoacetophenone (OAP), a potent avian repellent, on ingestive behavior of two rodent species, Prairie vole (Microtus ochrogaster), Deer Mouse (Peromyscus maniculatus Wagn.), and an avian species, European starling (Sturnus vulgarus L.) utilizing similar experimental conditions to facilitate inter-species comparisons. All three species avoided OAP-treated food. Apple consumption by voles was decreased from a baseline of theoretical zero% by OAP (0.01-10.0 ml liter -1 ), P < 0.00001, while mice avoided all but the lowest concentration of OAP (0.01-10 ml liter -1 ), P < 0.00001. A repellent should elicit avoidance behavior prior to the animal having physical contact with the commodity, ideally producing aversion via volatile cues rather than through direct contact. Therefore, we utilized two delivery methods for presentation of the test solutions to evaluate the repellency of OAP in the presence and absence of direct contact. Apple consumption by birds following exposure to OAP by either direct contact or volatile cues differed from a baseline of theoretical zero% consumption, P < 0.001. When birds had access to OAP through both direct and volatile exposures, reduction in apple consumption by European starlings was greater than observed following contact with the compounds volatile cues alone, P < 0.03. These findings argue against a major role for olfaction or naso-trigeminal chemoreception in avoidance of OAP-treated food. Instead, taste or oral trigeminal chemoreception appear to mediate responding.