Behavioral Evidence for "Contextual Decision Hierarchies" In the Hermit Crab, Pagurus samuelis

<p>In this dissertation, I examined how motivation and sensory cue perception influence the behavioral choices of hermit crabs. I began by reviewing behavioral experiments that have demonstrated the underlying sensory processing of visual, chemical, and tactile information in crustaceans and propose a novel behavior model entitled "Contextual Decision Hierarchies" in which sensory modalities vary in relative influence on behavior depending on context. This behavioral model was tested in a series of four experiments. In the first experiment, I tested whether the hermit crab, Pa gurus samuelis, deprived of food, shells, or both will respond differently from control hermit crabs when presented with food and shells concurrently. Differences in the number of contacts with each resource and the time elapsed before choosing a resource confirmed that deprivation increased motivation to acquire either food or shells. Results further indicated that being shell-less is a stronger motivation than being starved, such that finding shelter takes priority over finding food when both are needed. Next, I examined the relative influence of sensory information on shell acquisition behavior of hermit crabs by presenting visual, chemical, and tactile cues of shell availability in a factorial manner to hermit crabs removed from their shells. During shell acquisition, tactile cues were primary while visual and chemical information was secondary. In the third experiment I tested the relative influence of the same sensory modalities on foraging behavior. In contrast to shell-seeking, chemical cues were primary in food acquisition while visual and tactile cues were secondary. In both of these experiments, even though primary cues elicited the shortest decision times, in the absence of the primary cue, secondary cues could still be used to make appropriate decisions, albeit with significantly longer decision times. In the final experiment, I investigated the relative influence of visual, chemical, and tactile cues of the predator, Pachygrapsus crassipes, on anti-predatory behavior of the hermit crab, Pa gurus samuelis. Results indicated that visual cues are primary in detecting and avoiding predators, while chemical and tactile cues are secondary. These experiments suggest that for the hermit crab, Pa gurus samuelis, information is arranged in Contextual Decision Hierarchies.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biology

Year

2008

Author dc:creator

• Billock, Wendy Lee

Contributors dc:contributor

• Stephen G. Dunbar
• Leonard R. Brand
• Ronald L. Carter
• L. James Gibson
• William K. Hayes

• Biology
• Pagurus samuelis; Adaptation (Biology); Decision-making; Behavior modification.

Statement dc:rights

• This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Language dc:language

English

Repository record dc:identifier

https://scholarsrepository.llu.edu/etd/665

OAI identifier oai:identifier

oai:scholarsrepository.llu.edu:etd-1674