Shelter sharing and chemical courtship signals in the lobster Homarus americanus

In a 3.7-m Y-maze flume study of social odor-mediated behavior of mature lobsters (Homarus americanus), females preferred male- but not female-occupied shelters over empty shelters: they detected them from a distance and spent much time trying to enter. Males did not show distant detection and preference for female shelters but did spend much time trying to enter female but not male shelters once nearby. Sheltered resident males showed strong aggression toward visiting males but only mild aggression to visiting females; intermolt and premolt females could enter resident male shelters, cohabit for at least 7 h, receive mating attempts, and sometimes mate. Premolt females or females with sperm plugs resisted mating attempts. Visiting females released more than four times and males more than seven times as much urine during a shelter approach compared with an equal time in isolation. Females with or without urine release entered male-occupied shelters successfully, but mating attempts rarely occurred when female urine release was blocked. Female urine block resulted in greatly increased resident male aggression toward her, reaching the same levels elicited by visiting males with or without urine block. The results show that female urine signals reduce male aggression and facilitate mating.