Taste preference tests, with simultaneous presentation of treated and untreated food, were administered to 24 common vampire bats (Desmodus rotundus). The bats received brief exposures to four different stimuli representing sweet, salty, sour, and bitter tastes, each at four different concentrations. Despite a strong location bias, the bats significantly (P < 0.01) avoided the highest concentrations of the salty, sour, and bitter tastes. Consumption of the sweet stimulus at all concentrations was similar to that of the untreated standard. Vampires evidently can discriminate based on taste, although their ability is apparently poorly developed when compared with some euryphagous species such as the rat. Hence, taste is probably not a factor in host selection by the vampire.

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The methods of single stimuli and constant stimuli were used with a modified conditioned suppression technique to determine olfactory intensity-difference thresholds in White Carneaux and White King pigeons. While responding for grain reinforcement on a VI 2-min. schedule, conditioned suppression was established in the birds after several sessions by pairing amyl acetate odor at 7% of vapor saturation with electric shock. The degree of suppression to nonshocked lower intensities of this odor determined the DLs. Weber fractions computed, from these values ranged .6-7. Both psychophysical methods produced identical DLs. Olfactory nerve section abolished the 7% intensity response in all birds, showing that odor was the only cue utilized by the birds during preoperative discriminations.

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