Lobsters are also good models for studies on aggression. These fights have extremely interesting consequences for the combatants. If a previously-fought lobster is then placed into another staged fight, its behavior is dependent upon its status from the previous fight. In other words, previous losers lose or refuse to fight with a new opponent. In the case where losers are pitted against other losers, no fights occur.
Winners again win, unless they are pitted against another winner.
In that case, the fights escalate and the lobsters cause extensive damage to each other. Usually the dominant or subordinate status only lasts until the animal molts. Then, if a subordinate molts first, survives, and becomes larger than the dominant, it will often become the new dominant animal. These seemingly long-term changes in status and behavior are determined by the level of two hormones known as serotonin and octopamine. Winners have higher blood levels of serotonin, while losers have higher levels of octopamine.