Summary: The Sydney octopus (Octopus tetricus) occurs in unusual numbers on a shell bed of its prey remains that have accumulated as an extended midden where additional octopuses excavate dens. Here, O tetricus are ecosystem engineers, organisms that modulate availability of resources to other species and to their own species by causing physical state changes in materials. A community of invertebrate grazers and scavengers has developed on the shell bed. Fishes are attracted to the shell bed in numbers significantly greater than in nearby habitats. Large predators, including wobbegong sharks, were attracted to and fed on concentrations of fish, inhibiting the activities of the original engineers, the octopuses. Positive feedbacks included the accumulation of shell debris, increasing shelter availability for additional octopuses and aggregating fish. Negative feedbacks included reductions of nearby prey size and availability, aggression among octopuses, and predator limitation to octopus activity that would otherwise maintain the shell bed.
David Scheel, a biologist at Alaska Pacific University; Peter Godfrey-Smith, a philosopher of science who has appointments at City University of New York and the University of Sydney; and Matthew Lawrence, an Australian diver, collaborated to record interactions between common Sydney octopuses off the Australian island of Tasmania.
Their method was to put cameras on the sea floor in areas where there were plenty of these octopuses and then comb through hours and hours of video.
They aren’t done yet, but Dr. Scheel presented some of their initial findings in Anchorage at the annual meeting last month of the Animal Behavior Society, and they have about two dozen examples of octopuses signaling their aggressive intent.
Congrats on the awesome coverage -- and thank you for acknowledging the community, and for being a part of it!without tonmo i probally never would have made the inital contact with PGS and then david Scheel , and Stefan ... so well done. to this forum and the moderator.
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