Evidence for homing behavior in the American lobster Homarus americanus (H. Milne Edwards, 1837) (Decapoda: Astacidea: Nephropidae)

We used a high-resolution ultrasonic telemetry system to test the hypothesis that American lobsters, Homarus americans (H. Milne Edwards, 1837), are capable of homing behavior. Experiments were undertaken within an enclosed 50 m x 50 m mesocosm, which was constructed underwater in a cove along the New Hampshire coastline. The mesocosm prevented lobsters from moving out of range of the telemetry array and kept them confined to an area with a sandy substrate, with few potential landmarks. A total of 41 lobsters were fitted with ultrasonic tags, released within the mesocosm, and then tracked with a Vemco VRAP system that provided a position for each lobster every 2 min, with a resolution of similar to 2m. Typically, 1-3 lobsters were captured at a time, tagged, and tracked for three to five days. On 320 occasions, 37 of the lobsters left their home shelter, wandered > 200 m for several hours, and then returned to the same shelter. Twenty-five of the 37 lobsters expressed very clear homing events on 60 occasions, during which they moved at least 10 m away before returning within 12 hrs. In these events, homeward-bound trips were shorter than the outward-bound excursions, suggesting that lobsters might have knowledge of the position of their shelter relative to their location when they started the homeward journey. Many (113/320 or 35.3%) of these excursions took place at night, indicating that some other still undetermined cues, besides vision, might be involved in lobster horning behavior.