We've long been fascinated by cephalopods, in no small part due to their incredible abilities to change their appearances in fantastically diverse and often exceedingly strange ways. There are various types of squid that can change colors in seemingly psychedelic patterns, and we've seen footage of octopuses making themselves look like sea snakes, tiger fish, and various other creatures in attempts to fool predators (okay, we watch a lot of the Discovery channels). Despite having seen all of these examples, we were still pretty impressed when we saw that two species of octopus had been observed engaging in some very interesting camouflage techniques. As reported by the UC Berkeley News:

Two species of tropical octopus have learned a neat trick to avoid predators — they lift up six of their arms and walk backward on the other two.

This first report of bipedal behavior in octopuses, written by University of California, Berkeley, researchers, will be published in the March 25 issue of Science.

When walking, these octopuses use the outer halves of their two back arms like tank treads, alternately laying down a sucker edge and rolling it along the ground.

...

[UC Berkeley graduate student Crissy] Huffard and coauthor Robert Full, professor of integrative biology at UC Berkeley, think that this bipedal walking is a strategy octopuses use to backpedal away from predators while remaining camouflaged. Octopuses camouflage themselves by changing both color and shape, but when startled and forced to move quickly, they have to give up their camouflage.

Not so when walking.

"This bipedal behavior allows them to get away and remain cryptic," said Huffard.

One species, Octopus aculeatus from Indonesia, seems to be emulating sea algae by raising six arms while quickly walking away on the other two. See the Quicktime video (screen cap below) at Science Magazine, or at UC Berkeley News.

The other, Octopus marginatus of Australia, who lives in an area in which numerous sunken coconuts are scattered across the sea floor, wraps six arms around itself in an apparent attempt to look like a coconut, while scuttling away on the other two. See the Quicktime video (screen cap below) at Science Magazine, or at UC Berkeley News.

In addition to the "neat" factor, there are possible applications in the field of robotics:

Full, who looks at many types of animal locomotion and seeks to determine how animals control such movements, sees a revolutionary new principle in how the octopus uses its arms - one that could be used in making soft, squishy robots.

"Understanding behavior like this could usher in a new frontier of 'soft' robotics," in contrast to the rigid robots common today, he said.

"New artificial muscles that can stiffen at will could reproduce this walking behavior," said Full. "The wonderful thing about soft robotics is that it's infinitely adaptable, unlike the few degrees of freedom of rigid robots."

For more details, check out the article in the UC Berkeley News, the article in NewScientist, both of which we found via The Octopus News Magazine Online. Also, as noted above, the full story appears in the March 25 issue of Science. From that site, you can read the paper online (paid subscription required), and also see the videos above (for free).

Of course, no post about octopus behavior would be complete without a nod to PZ Myers of Pharyngula, the Don Corleone of the Cephalopod family, who also comments on this story.

"Friday Ark" from Modulator

Cats, Dogs, Spiders and ? every Friday. I'll post links to sites that have Friday (plus or minus a few days) photos of their chosen animals as I see them (photoshops at my discretion and humans only in supporting roles). Leave a comment or trackback to... [More]