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  • Author or Editor: Brian A. Hazlett x

Brian A. Hazlett

Abstract

The distances at which individual hermit crabs (Clibanarius tricolor and C. antillensis) showed agonistic behavior patterns was recorded after the animals had been held at one of two densities for a week. 1) Behavior patterns differed significantly in the average distance of separation when they were executed. 2) For almost all patterns, there was considerable variability in the distances at which they were shown. 3) Part of this variance in distances was due to the behavior of the other crab. 4) Density treatment affected the distances at which behavior patterns were shown, the crabs held at the lower density having greater distances. Apparently as a result, lower density crabs lost more interactions. 5) The distances at which behavior patterns were shown were not correlated with either absolute or relative size of the acting crab. 6) Comparison of distances in intraspecific and interspecific interactions indicated very similar behavior in the two species, except that C. antillensis was not as clearly affected by the density treatment.

Brian A. Hazlett

Abstract

Cine films of the movements of the spider crab Microphrys bicurnulus during walking, feeding, and agonistic interactions were analyzed. 1. The variability in final position of ambulatory leg movements (displays) executed during agonistic interactions was significantly less (F = 2.29, p < 0.05) than the variability in final leg position during walking. 2. The variability in final position of cheliped movements (displays) executed during agonistic interactions was significantly less (F = 2.21, p < 0.05) than the variability in final cheliped position during feeding. 3. There was no significant decrease in temporal variability between non-display and display movements.

Brian A. Hazlett

Abstract

Chemical stimuli were presented to individuals of the hermit crab Diogenes avarus to determine the nature of the interactions between stimuli that elicit conflicting responses. The odour of degraded snail flesh (a signal associated with potential empty shells) elicited an increase in both locomotion and the rate of grasping of gastropod shells. The odour of a visual predator (Matuta lunaris) elicited a cessation of locomotion by the hermit crabs. When snail flesh odour was presented in combination with various strengths of the predator odour (5% to 100%), the responses tended to show a step-function relationship to stimulus strength. Predator inhibition of snail-induced grasping dominated until predator strength was just 5% of full strength odour. However, 5% predator odour alone induced a response similar to full strength predator odour. In the case of locomotion, snail-induced increases predominated no matter what the strength of the predator odour. For both behaviours, responses of hermit crabs tended to be hierarchical rather than graded.