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.
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