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- Apr 13, 2005
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- 76
i think yes
A few months ago I wrote about Octopolis, a site at Jervis Bay, Australia where octopuses have been living continually at high density for several years now. The site was discovered by Matt Lawrence, and we published a paper about it earlier this year.
I’ve made two trips back since that post. The first trip was in October, with Matt and David Scheel, a marine biologist from Alaska who is an expert on the Giant Pacific Octopus. On that trip we started, under David’s guidance, looking also at the broader ecology of the site. There seem to be unusual numbers of many species gathering there – rays and baby sharks, hermit crabs, and starfish. Above hover squid and schools of fish.
A few days ago Matt and I went out there again just to see how things are.
As soon as we arrived we saw octopuses everywhere, with very few of them minding their own business. It was the most interaction I have seen. They were wandering, boxing with their arms, displaying, jetting about. When I tried to measure things I had to wrestle over the tape.
We leave video cameras on weighted tripods at the site to film what happens when we’re not there. The octopuses were in no mood to leave them be. All three cameras were knocked over and dragged around, lead-weight legs and all. That is what’s happening in the first photo above; it’s a frame from a sequence on one camera of another camera being hauled by an octopus into its den, for an attempt at total destruction.
A longer version, with attempts to eat the camera, is here [... to come].
After the octopus here had given up on the first camera and lugged it back out from its den, the other octopus, on the left, attacked the camera that filmed the first sequence.
A good day at Octopolis.
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.
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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.
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