Aggressive behaviour of spotted spiny lobsters (Panulirus guttatus) in different social contexts: the influence of sex, size, and missing limbs

Abstract

AbstractPanulirus guttatus is a sedentary spiny lobster that exhibits cryptic behaviour and a low degree of gregariousness. Because these lobsters are obligate coral reef-dwellers and avoid sandy expanses, they are potentially distributed in relatively small, discrete populations with variable social contexts, which can strongly influence the expression of aggression. The present study examined the relative importance of sex, size, and the number of missing limbs in the shelter-related aggressive behaviour of replicated groups of four lobsters that differed in social context (i.e. same-sex and mixed-sex groups). Each group was held in a seawater tank with a single artificial cave-like shelter. The interior of the cave was video-recorded for 72 h and the number of aggressions performed by each individual was quantified in a 10-min segment of video per hour. Most aggressions were related to occupancy of the shelter inner space and tended to end when individuals were sufficiently spaced out. In general, per-capita rates of aggression were higher at night and size was an important predictor of aggressiveness among individuals of the same sex. Males were substantially more aggressive than females, but the number of missing limbs significantly impacted the degree of aggressiveness in males. In mixed-sex groups, fewer aggressions occurred when the largest individual was a male than when it was a female, suggesting that it may take longer for smaller males to assert themselves. Our results provide insights into some potential consequences of increase in fishing pressure and loss of habitat complexity in Caribbean reefs for the social behaviour and population dynamics of these lobsters.