Shell and food acquisition behaviors: Evidence for Contextual Decision Hierarchies in hermit crabs

Shell and food acquisition behaviors of the hermit crab, Pagurus samuelis, were examined in response to cues of shell and food availability. Tactile, visual, and chemical cues were presented in a factorial manner, and time was measured between initial contact and either inhabitation of a shell or initiation of feeding. We considered the time difference between initial contact and subsequent behavior to be a measure of hermit crab 'decision time'. For shell acquisition experiments, treatments that included tactile cues elicited significantly shorter decision times (8.5-117.1. s), than treatments without tactile cues (294.5-765.2. s). In contrast to the shell acquisition experiment, we found that in food acquisition experiments, treatments that included chemical cues elicited significantly shorter decision times (78.4-450.5. s), than those without chemical cues (570.0-778.1. s). Although primary cues elicited the shortest decision times during foraging and shell-seeking, in the absence of the primary cue, secondary cues could still be used to make appropriate decisions, albeit with significantly longer decision times. Therefore we propose that hermit crabs sort environmental information in 'Contextual Decision Hierarchies' in order to make accurate and efficient behavioral choices.