Olfactory discrimination in a captive turkey vulture (Cathartes aura)

Abstract

Birds are not known for their sense of olfaction; in fact, until recently it was thought that all birds had a markedly poor sense of smell in comparison to mammals. Recent studies, however, have proven otherwise. Although only a select few birds species have been found to rely heavily on olfaction for food and nest location, a sense of olfaction is by no means absent in birds. There have been numerous studies on avian olfaction but to date there have been no studies directly testing a turkey vulture’s ability to use olfaction in a discrimination task, and the methods employed in other studies on this subject are inconclusive. By utilizing a behavioral olfactory discrimination task, this study aims to test a thirteen-year-old captive turkey vulture’s use of his sense of olfaction to discriminate between visually identical unscented and peppermint scented containers. In a preliminary study, Stan performed well above chance levels during every session of a visual discrimination task. Similarly, results of an olfactory discrimination task indicate that Stan chose the correct container (scented with peppermint extract) significantly more often than the unscented container. Although a right side bias was initially observed and although Stan adopted a win-stay-lose-shift strategy, those strategies were eliminated with the introduction of negative punishment. Stan was successfully able to use olfaction as cue to earn a food reward; however, he did not appear to develop an effective discrimination learning set and he did not generalize well from one stimulus type to another. These results suggest that wild turkey vultures may also be able to use odorants as a cue to find food or discriminate between carrion at different stages of decomposition, and that they may be similarly predisposed to use simple heuristics (i.e., win-stay-loseshift) when faced with cognitive challenges.