A Clever Chameleon of the Sea
“The octopus, O horror! inhales a man. It draws him to itself, and into itself; and, bound, immobile, he feels himself slowly ingested by that incredible being which is the monster.”—TOILERS OF THE SEA, BY VICTOR HUGO.
THE octopus has been the target of much bad publicity. Ancient myths and fanciful tales—like the one quoted above—have unfairly stigmatized the creature.
In reality, though, even the giant Pacific octopus, which may reach a length of some 20 feet [6 m] and weigh up to 110 pounds [50 kg], does not generally pose a danger to humans. In recent years fabulous legends regarding this eight-legged “monster” have been replaced by facts. Divers and marine biologists have learned much about the many varieties of octopus.
Capturing Prey and Avoiding Enemies
Rather than devouring humans, octopuses feed chiefly on crustaceans, employing their eight arms and as many as 1,600 muscular suckers to capture prey. Using these suckers, a small octopus is capable of dragging an object that is 20 times its own weight! Some octopuses also spray venom, which paralyzes their prey almost instantly.* The octopus then eats by pulling the food through its beaklike jaws.
What if the octopus finds itself the intended meal of another creature? It has a surprising disadvantage. Its pale blue blood, which relies on hemocyanin instead of hemoglobin, carries little oxygen. As a result, the octopus tires quickly. Yet, it has special skills to protect itself from seals, whales, and other predators.
One such skill is propulsion. When threatened, the octopus propels itself backward by expelling water from its thick mantle. This sly creature has another escape tactic. It may discharge an ink cloud, which contains a pigment that does not dilute in seawater. Thus hidden, the octopus can change direction and flee to safety before the cloud dissipates.
A Master of Disguise
Of course, the octopus prefers not to be pursued in the first place. How does it hide from predators? Famed underwater explorer Jacques-Yves Cousteau wrote: “At Marseilles, where our team began shooting the film on octopuses, most of our divers reported that there were no octopuses in the area; or, that if there had been some, they were no longer there. In fact, the divers were swimming right past the octopuses, who were so well camouflaged as to be practically invisible.” How did the octopuses manage this feat?
An adult octopus has up to two million chromatophores, or color cells—as many as 130,000 per square inch [200 per square millimeter]—in its skin. Each color cell contains a red, yellow, or black pigment. By contracting or relaxing the muscles around the cells, the octopus can flash a solid color or even colored patterns within a few seconds.
Ironically, it appears that the octopus does not have color vision. Yet, its range of skin colors goes far beyond three pigments. Iridocytes, cells containing mirrored plates, refract light to match the color of the octopus’ surroundings. That is not all. When hiding on a coral reef, an octopus can change texture by puckering its otherwise smooth skin into prickles, blending in with a similarly rough surface.
Dutiful Builder and Housekeeper
Not surprisingly, the home of an octopus can be hard to find. They tend to build their dens in crevices and under large rocks, using local building materials. The roof and walls of an octopus’ den may incorporate stones, bits of metal, shells, and even shipwreck remains and ocean litter.
Once its home is constructed, the octopus is a meticulous housekeeper. It shoots out water to smooth the sandy floor inside. After a meal, all food debris is pushed outside. To test the creature’s maintenance skills, Cousteau’s team of divers removed some of the stones from the wall of an octopus’ den. What did the octopus do? One pebble at a time, it slowly reconstructed the wall! Cousteau wrote: “The process continued until the wall was entirely rebuilt; and it was identical in every respect with that which the divers had demolished.” The octopus’ reputation for keeping its home neat and orderly is well-known. When divers see a den with accumulated sand or debris inside, they know it is vacant.
Her Last Home
In general, the last and most important home a female octopus will inhabit is her nesting den. After successfully receiving a sperm package from her mate and storing it until her eggs are released, she may spend several weeks looking for a suitable home. Next, she fortifies her nesting den and glues thousands of eggs, in clusters, to the roof. The blue-ringed octopus, however, builds no such den. Since her bright colors warn predators to stay away, she prefers to care for her young in the open sea, where she can advertise her venomous bite.
The octopus is a dutiful mother. After laying her eggs, she will likely refuse to eat. Instead, she protects her eggs, cleans and aerates them, fortifies her den, and takes on a defensive posture to ward off predators. Though the female octopus will die after her offspring are hatched, she cares for them right until the end. Cousteau said: “No one has ever reported that a female octopus left her eggs unprotected.”
In most species of octopus, tiny newborn hatchlings rise to the water’s surface as plankton. Many are eaten by other marine animals. After several weeks, though, the survivors return to the bottom of the sea and mature into full-grown octopuses, living up to three years.
How Clever Are They?
Some suggest that when used in connection with animals, the word “intelligence” involves the ability to learn from experience and solve problems. In that regard, consider this comment by Cousteau: “The octopus’ timidity is a reasoned reaction, one that is based primarily on prudence and caution. . . . If a diver is able to demonstrate that he means no harm, the octopus quickly loses its timidity—more quickly than any ‘wild’ animal.”
Octopuses have the most highly developed brain and eyes among invertebrates. Their eyes, like ours, can be finely focused and can adapt to changes in light. The optic lobe interprets information received from the eyes and this, along with an acute sense of touch, enables an octopus to make surprisingly clever decisions.
Several scientists report seeing an octopus learn to remove a stopper from a bottle in order to reach a crustacean inside. Others have reported that an octopus can figure out how to unscrew the lid on a jar in order to get at the food within. In Canada’s Vancouver Aquarium, an octopus disappeared nightly up a drainpipe to eat the fish in the neighboring tank.
Regarding the cleverness of the octopus, the book Exploring the Secrets of Nature concludes: “We are inclined to credit primates with the highest levels of intelligence, but there is proof that octopuses, too, are among the most intelligent of animals.”
The cleverness of octopus behavior may remind us of creatures that the Bible describes as “instinctively wise.” (Proverbs 30:24) They truly are a marvel of creation. Among scientists and divers alike, the “horror” of Victor Hugo’s imagination no longer taints the octopus. Those who study this creature are left with profound awe for this clever chameleon of the sea.
Only the blue-ringed octopus, native to Australia, is considered lethal to humans. Its bite can cause respiratory failure.
[Picture on page 15]
A blue-ringed octopus
© Jeffrey Rosenfeld
[Picture on page 16]
A Pacific reef octopus in perfect camouflage, directly below the mouth of a predatory fish. Can you see the octopus?
[Pictures on page 16, 17]
Octopuses come in many varieties and colors
[Picture on page 17]
Tiny hatchlings head for the surface
© Fred Bavendam
[Picture Credit Lines on page 16]
Top left: © Roger T. Hanlon; above: © Jeffrey Rosenfeld