Individuality in the predator defense behaviour of the crab Heterozius rotundifrons

Abstract

When individuals of the crab Heterozius rotundifrons are stimulated by tactile input they assume a rigid appendage-spread posture for a number of seconds. This posture is effective in reducing predation. When tested repeatedly, individuals both differed from one another in the duration of maintaining this posture and were consistent in their responses. This result held if crabs were tested five times in one day with the same stimuli (with either tactile input alone or tactile input + alarm odour), stimulated with three different sensory input combinations (tactile, tactile + alarm odour, tactile + alarm odour + shadows), or tested once a day with tactile input for five days. Crab sex and size were not important in explaining the variation in duration of this predator defense behaviour.