Ocean Watch

I saw the new Harry Potter movie last weekend. It's scarier than the others, featuring mermaid witches, people-eating bushes and a really mad dragon.

But the creatures that come closest to killing Harry are some octopus ogres, their writhing arms clamping onto the boy's skin to pull him to the ocean's depths.

Harry survives, of course, but the resulting suction-cup wounds on his neck and arms drive the point home: It was sucking, strangling octopuses that nearly killed our hero.

I hate it that octopuses are always the bad guys in movies. Sure, they have eight wiggly arms attached to a big squishy head that's topped with two bulging eyes. But consider the functions of these odd body parts and you'll find a lot to love.

Octopuses are the smartest of all invertebrates, with the problem-solving abilities of some birds and mammals. And they remember their lessons for weeks.

In one study an octopus was allowed to catch and eat a crab offered on a square background. Researchers gave the octopus a mild electric shock, however, if it went for a crab on a rectangular background.

After only a few of these sessions, the octopus got the message. Thereafter, the animal jumped onto squares even when no prey was present, and stopped attacking anything on rectangles.

Octopuses know their squares from their rectangles, but they cant figure out some shapes obvious to us. They don't, for instance, know a circle from a square.

Stick to squares though, and these creatures are geniuses. An octopus knows the difference between a square standing on its side and one standing on its corner. These animals can also distinguish between a 2-inch square and a 4-inch square, even when the bigger one is twice as far away.

Besides being brainy, octopuses also have excellent eyesight. From a distance of three feet, an octopus can discriminate between objects less than one-quarter of an inch big.

An octopus' sense of touch is good, but again, only in specific ways. Studies show that octopuses can distinguish with their tentacles texture and chemical differences of a surface. They can't, however, determine its shape.

One possible explanation for this deficiency is that tentacles have no divisions or structures, such as a thumb and forefinger, that could function as a unit of measurement.

Those tentacles have suction cups instead, efficiently handling whatever prey the octopus has captured.

In small octopuses the suction in these cups is easy on human skin. My scuba diving friends and I have all let Hawaii octopuses crawl on our bare arms, the curious animals feeling their way around to check us out. The suction cups pull off with little pops.

There are some species, however, that I would not want feeling my arm. Divers in the Sea of Japan have spotted octopuses with tentacles 30 to 45 feet long. Now that's spooky.

OK, I can see why filmmakers so often depict these squirmy, suckered, spineless blobs as monsters. But remember Shrek. Monsters can be lovable, too.