Den choice and occupation patterns of shelters by two sympatric lobster species, Panulirus argus and Panulirus guttatus, under experimental conditions

Abstract

Panulirus argus and P. guttatus are sympatric and commonly share dens. We studied their den-related behaviour in 3 m-diameter tanks, each holding a casita (low den) and a cave (high den) (1) separately (2) together (3) together with a triggerfish predator (Balistes vetula), and (4) separately with the predator. Most P. argus left shelter at night, and some during the day, and showed no den preference in any treatment. In caves, individual P. argus occupied all parts of caves in treatments 1 and 2 and mostly the vault (walls and ceiling) in treatments 3 and 4. Not all P. guttatus left shelters at night, and none during the day. Individual P. guttatus showed no den preference in treatments 1 and 2, preferred the cave in 3 and 4, and always preferred the cave vault. Presence of congeners did not affect den choice or cave position for either species, whereas the predator affected den choice (P. guttatus only) and position in caves (both species). Videotapes showed aggression between individual P. guttatus but not between individual P. argus or between species. The fish cohabited with lobsters in the casita but attacked them in caves and in the open. Unlike P. argus, P. guttatus exhibited no communal defence.