Social organisation and den utilisation of painted spiny lobster (Panulirus versicolor) on a coral reef at Northwest Island, Australia

Abstract

The social ecology of spiny lobsters (Palinuridae) is poorly known but important for understanding their evolution and interpreting the behavioural basis of their catchability. Visual surveys of 60 ha of coral reef at North-west Island revealed 34 shelters (dens) occupied by painted spiny lobster (Panulirus versicolor). Eighty-five lobsters were tagged with highly visible external tags and moult-resistant internal tags. Most dens contained only a single lobster, but the distribution of lobsters was aggregated; most lobsters occurred in groups of 2–7 individuals. Daily visits to each den revealed that lobsters moved frequently to and from nearby dens and the composition of groups changed often. However, groups were not random mixtures of individuals since two male lobsters never occupied the same den simultaneously. Surprisingly, there was no significant relationship between body size and male social status (number of co-habiting females). Experimental translocation of single male and female lobsters to occupied dens did not result in eviction, regardless of body size, indicating that subtle mechanisms drive this social system. Most lobsters congregated in the same 10–15 dens. This renders P. versicolor easy to find and vulnerable to over-exploitation, but suggests that marine reserves may be useful for protecting this highly sought-after species.