Shelter-related aggression between adult male conspecific intruders and resident maternal American lobsters (Homarus americanus) with eggs at different stages of embryogenesis

It has recently been shown that maternal (ovigerous/hatching) American lobsters (Homarus americanus) reliably out-compete non-maternal females for shelters. It is also known that nonmaternal females are subordinate to male conspecifics. To complement those studies, this maternal status effect on aggression was evaluated using intruding conspecific males. Resident maternal females were used whose eggs were at mid-embryogenesis, late-embryogenesis/hatching, or were 3-4 weeks post-hatching (non-maternal). The males reliably evicted resident females at all three stages. This male shelter competition advantage over maternal females is most likely produced by a combination of the necessity of the possession of a shelter by males for mating purposes, and the low shelter fidelity of ovigerous females due to their continual migratory behavior during the 9-12 month period of embryogenesis.