Does gregariousness function as an antipredator mechanism in the Mediterranean slipper lobster, Scyllarides latus?

Abstract

The possible antipredation benefits of group living have been difficult to study in species where the size and incidence of groups are beyond the investigator’s control. A field test with tethered Mediterranean slipper lobsters, Scyllarides latus, revealed that attack and capture rates for solitary individuals did not differ significantly from those for grouped individuals after either 3 or 24 h of exposure to potential predators. Although predator attack rates on grouped and solitary lobsters also did not differ after 3 h, they were significantly higher on groups than on solitary lobsters after 24 h. Differences in fish behaviour during the first hour of lobster exposure suggest that confusion effects played a role only initially and, presumably, conferred a short-lived advantage on clumped prey. Confusion effects were represented by a higher frequency of passes and reapproaches for fish concentrating on grouped lobsters and a lower frequency of bites. Attacks were more directed for fish concentrating on solitary lobsters. With increasing exposure time, however, groups may have served to facilitate predation because triggerfish (Balistes carolinensis) were equally successful at capturing grouped and solitary lobsters.