Dominance, territoriality and mating in the lobster,Homarus americanus:A mesocosm study

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Abstract
A semi‐natural benthic hatitat for the lobster, Homarus americanus was created in the 180 m2 pool tank at Dalhousie University. This large tank accommodated 30 lobsters which were studied using focal and census observations to determine the relationship between social dominance, use of space and mating. Approach‐retreat sequences were used to establish dominance, and the frequency of high‐level aggressive acts was much lower than in previous studies in smaller tanks. Large males initiated agonistic interactions much more frequently than did other categories of lobsters, particularly directing their attention to other large males and large females. Individuals were more likely to win interactions with otherwise dominant individuals if they were defending their own shelter, suggesting a form of shelter‐based territoriality. In addition, dominant individuals often kept shelters immediately adjacent to their own free of other lobsters. The most dominant male in the tank attempted to extend his territory to include four widely‐spaced shelters which were large enough for mating. He frequently evicted other males from these shelters and disrupted their cohabitations With premolt females. Females sought out males in the mating shelters prior to their molt, but showed a substanial degree of “fickleness.”; Individual females initially moved in with several of the top‐ranking males before choosing one for cohabitation, and then occasionally abandoned their mate to take up cohabitation with other males nearby. This behaviour emphasizes the importance to the males of establishing dominance and attempting to clear the area of competing males.