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.

LLU Discipline





School of Science and Technology

First Advisor

Stephen G. Dunbar

Second Advisor

Leonard R. Brand

Third Advisor

Ronald L. Carter

Fourth Advisor

L. James Gibson

Fifth Advisor

William K. Hayes

Degree Name

Doctor of Philosophy (PhD)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

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



Page Count

xii: 155

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage 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.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives

Included in

Biology Commons