Honors Theses


Karolyn Hansen, Ph.D.



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Honors Thesis


Predation is a major source of mortality for prey, which creates a selective pressure to avoid predators whenever possible. By using alarm cues produced by conspecifics, individuals can be alerted of nearby predators without coming into direct contact with them. However, whether individuals can distinguish between different conspecific cues or whether some cues might indicate a more severe predation threat than others is not known. Studied was the three-spined stickleback’s ability to distinguish between environmental cues by exposing conspecifics to four different treatments in a randomized order: 1) Control (control olfactory cues with an unexposed demonstrator), 2) Visual Only (control olfactory cues with an exposed demonstrator), 3) Visual and Stress (stress cues with an exposed demonstrator), and 4) Visual, Stress, and Damage (stress and damage cues with an exposed demonstrator). For five minutes before and after exposure to the cues, I watched for four key defensive behaviors: hiding in plants, hiding in the gravel at the bottom of the tank, thigmotaxis, and shoaling. Directly after each assay, the focal subject was placed in 200 ml of RO water in a 600 ml beaker for one hour to collect waterborne cortisol. Observer hiding behavior increased when observers were exposed to visual cues of stressed conspecifics paired with either olfactory cues of stressed conspecifics or conspecific stress and damage cues. Observers also shoaled less when exposed to visual cues paired with olfactory stress cues, but not with visual cues alone, or visual cues paired with stress and damage cues. Males shoaled more than females but hid less. No change in behavior was observed for demonstrators, regardless of what cues were added. Also, no differences in waterborne cortisol levels were measured for each of the treatments.

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Undergraduate research