The Octopus: The Intelligent Invertebrate

(From Creatures of the Sea, available online Kids InfoBits, which includes ReadSpeaker text-to-speech technology)

As animals go, octopuses are quite intelligent. They have been showing their smarts for centuries by stealing fish out of nets and lobsters out of traps. In recent decades, octopuses have been the subjects of many scientific studies designed to gauge their intelligence. Scientists now agree that octopuses are probably the smartest of all invertebrates.

Signs of Intelligence

Just how smart is an octopus? No one knows for sure. Some scientists think octopuses may be about as intelligent as house cats. But other scientists point out that an invertebrate's brain is not like a vertebrate's brain, so intelligence may mean something very different in an octopus than it does in a bird, reptile, or mammal.

Still, there is no denying that octopuses do some smart things. For instance, some octopuses have learned to recognize divers who visit them regularly. And they remember these divers for a long time. Even if a diver visits only once in a while, the octopus will approach without fear — a sure sign that the diver looks familiar.

Octopuses in one aquarium were even seen playing. The octopuses used their funnels to squirt jets of water at an empty plastic bottle, pushing it back and forth. Until this behavior was observed, scientists thought that only vertebrates were smart enough to play. These playful octopuses were doing more than just squirting water at a bottle, though. They were showing signs of intelligent behavior.

Problem Solvers

The ability to solve problems is another sign of intelligence. Several experiments have shown that octopuses have this important ability.

In one famous experiment, scientists put a live lobster inside a see-through glass jar. Then they plugged the mouth of the jar with a cork and put it near an octopus's home. The octopus came out immediately and started trying to eat the lobster. First it grabbed at the lobster with its arms, but it was blocked by the glass of the jar. So the octopus tried another hunting technique. It wrapped the entire jar in its web, then tried to poison it.

This did not work either. But the octopus did not give up. It kept trying to get the lobster. After about three hours, the octopus finally pulled the cork out of the jar. Within seconds, the hungry octopus had grabbed the lobster and started eating it.

It is possible that the octopus pulled the cork out by accident. But the scientists who ran this experiment do not think so. They believe that the octopus figured out how to release the lobster from the jar. The octopus learned that its normal methods would not work, and it kept trying new things until it finally accomplished its task.

Octopus vs. Human

Using their natural intelligence and their soft bodies, octopuses are escape artists. They can find the tiniest crack in an aquarium top, then squeeze themselves through it to freedom.

Once out of the tank, the octopus moves toward open water. If there is no open water, the octopus may just crawl around making trouble. In one case, an octopus escaped from a home aquarium and crawled into a nearby study. The owner found the octopus pulling books off the shelves and flipping through their pages.

Another interesting case occurred at a large public aquarium. Employees noticed that animals were disappearing from the tanks during the night, so they put up a video camera to see what was going on. They discovered that an octopus was climbing out of its tank and into the other animals' tanks. The octopus would eat its fill, then return to its home.

In the morning, the thief was always found right where it belonged.

This kind of behavior fascinates scientists. It makes them want to learn more about octopuses and their amazing intelligence. However, it is not easy to study octopus behavior. An octopus brain works very differently from a human brain, so understanding the octopus well enough to design good experiments is a challenge. The octopus's short life span is another challenge. Small- to medium-sized octopuses do not live long, so scientists may have only a few months to work with any individual animal.