Mysteries of the Octopus

Forty years ago, Jennifer Mather was diving off the coast of Bermuda in the Atlantic Ocean. She spotted a common octopus, a soccer ball-sized octopus found in oceans around the world. Mather watched it slink around the seafloor, using the suckers on its eight long arms to gather clams and snails. The octopus dragged the morsels of food to its den, cracked open the shells with its arms, and began eating. 

When the octopus was finished, Mather watched it do something surprising. It scuttled out of the den and used one of its arms to pick up a rock. It brought the rock to its den, then left to grab another, then another. It lined the rocks up in a row so they formed a wall over the den opening. “That was my ‘aha’ moment,” remembers Mather. “Octopuses are smart!”

Today, Mather studies animal behavior at the University of Lethbridge in Canada. She designs experiments to investigate how octopuses think. Scientists consider octopuses some of the most intelligent invertebrates. Scientists like Mather want to better understand the animals’ remarkable abilities—and how those abilities help them survive.

Forty years ago, Jennifer Mather was diving off the coast of Bermuda. It’s an island in the Atlantic Ocean. She spotted a soccer ball-sized common octopus. Mather watched the animal slink around the seafloor. The octopus has suckers on its eight long arms. It used them to gather clams and snails. It dragged the food to its den. There, the octopus cracked open the shells and began eating. 

Then the octopus did something surprising. It crawled out of its den. It picked up a rock and brought it back. Then it grabbed another and another. It lined the rocks up. They formed a wall over the den opening. “That was my ‘aha’ moment,” remembers Mather. “Octopuses are smart!”

Today, Mather works at the University of Lethbridge in Canada. She studies animal behavior. Mather designs experiments to investigate how octopuses think. They are thought to be some of the smartest invertebrates. Scientists like Mather want to learn about the animals’ amazing abilities.

There are about 300 species of octopuses living in oceans around the world. They nest in rocks and reefs and hunt crabs, fish, snails, and clams. The tiniest species, the star-sucker pygmy octopus, is about the size of a golf ball. The largest, the giant Pacific octopus, can grow to be up to 6 meters (20 feet) across arm-to-arm!

Like all invertebrates, octopuses are boneless. But unlike clams and snails, they have no hard shells. Their squishy bodies make them a tempting meal for predators like eels and sharks. “Everybody’s out to get them,” says Mather. 

Octopuses have many adaptations to help them evade their enemies. One is their talent for camouflage. Many octopuses can change colors to match their surroundings (see Masters of Disguise, below). A predator might swim by without noticing an octopus is there!

About 300 species of octopuses exist around the world. They nest in rocks and reefs. They hunt crabs, fish, snails, and clams. The tiniest species is the star-sucker pygmy octopus. It’s about the size of a golf ball. The largest is the giant Pacific octopus. It can grow to be up to 6 meters (20 feet) across arm-to-arm!

All invertebrates lack bones. Some, like clams and snails, have hard shells. But an octopus’s body is totally squishy. That makes octopuses seem like a tempting meal for predators like eels and sharks. “Everybody’s out to get them,” says Mather. 

Octopuses have adaptations to help them survive. One is their talent for camouflage. Many octopuses can change the color of their skin. They do so to match their surroundings (see Masters of Disguise, below). A predator might swim by without even noticing an octopus is there!

Octopuses can also squish their flexible bodies into crevices. If no hiding spot is available, some octopuses make their own. In the Western Pacific Ocean, the veined octopus picks up coconut shells that fall into the water. It carries the shells while it hunts, then pulls them over itself to hide if a predator is near. 

Very few animals use natural objects as tools in such clever ways, says Piero Amodio, a biologist at the Anton Dohrn Zoological Station in Naples, Italy. “It’s surprising how complex the behavior of octopuses can be.”

Octopuses can also squeeze into tight spaces to hide. Some octopuses even make their own hiding spots if there are none. The veined octopus is found in the Western Pacific Ocean. It picks up coconut shells that fall into the water. It carries the shells while it hunts. Then it pulls them over itself to hide if a predator is near. 

Few animals use objects as tools in such a clever way, says Piero Amodio. He’s a biologist at the Anton Dohrn Zoological Station in Naples, Italy. “It’s surprising how complex the behavior of octopuses can be.”

Scientists don’t all agree on what makes an animal intelligent. But the ability to use tools, solve problems, and learn new skills are considered signs of being smart. Researchers have observed chimpanzees, crows, and dolphins doing these things. These animals have large brains for their bodies, and octopuses do too. 

But in other ways, octopuses are unique. Their nervous system works differently from those of other clever species. In most intelligent animals, including humans, the brain contains the majority of neurons. An octopus has only one-third of its neurons in its brain—the rest are in its arms!

This unusual arrangement helps an octopus hunt. Its sensitive suckers let it feel for prey quickly. Having so many neurons allows each arm to react on its own without waiting for instructions from the brain.

Scientists don’t all agree on what makes an animal smart. But there are a few things they look for. They include using tools, solving problems, and learning new skills. Scientists have seen chimpanzees, crows, and dolphins doing these things. These animals have large brains for their bodies. And octopuses do too. 

But an octopus’s nervous system doesn’t work like those of other clever species. The brain contains most of the neurons in most smart animals, including humans. But an octopus has only one-third of its neurons in its brain. The rest are in its arms! That allows its sensitive suckers to feel for prey quickly. The arms can react on their own. They don’t have to wait for directions from the brain.

Most intelligent animals live in groups. Their big brains likely help them communicate and work together to survive. But octopuses spend most of their time alone. And unlike most intelligent animals, their life spans are very short. Most species live just one or two years. That leaves scientists wondering: How did their unusual intelligence evolve?

Most smart animals live in groups. Their big brains likely help them communicate and work together to survive. But octopuses spend much of their time alone. And their life spans are very short compared with those of other smart animals. Most octopus species live just one or two years. That leaves scientists wondering how the animals evolved to be so smart.

There are many questions scientists still have about octopuses. Amodio has studied whether octopuses can learn from each other the way many other intelligent animals do. To find out, he has given octopuses food sealed inside jars to see if they could open them. The octopuses opened the jars faster if they had watched another octopus do it first.  

Mather is interested in how playful the animals are. She once floated plastic pill bottles in octopuses’ tanks to see how they would respond. Two octopuses let the bottle drift toward them, then sprayed water to push it across the tank. They did this over and over—like they were bouncing a ball!

Octopuses’ cleverness can pose problems for people keeping them in labs or aquariums. Sometimes they find ways to escape! Octopuses are full of surprises, but that makes them fun to work with, says Amodio. Plus, there’s a lot left to discover about their intelligence. “We hardly know anything about them,” says Mather.

Scientists still have many questions about octopuses. Many smart animals can learn from each other. Amodio has studied whether octopuses can too. He has given octopuses food sealed inside jars. He wanted to see if they could figure out how to open them. The octopuses opened the jars, and they could do it faster if they watched another octopus do it first. 

Mather is interested in how playful the animals are. She once floated plastic pill bottles in octopuses’ tanks. Then she watched to see how they’d react. Two octopuses let a bottle drift toward them. Then they sprayed water to push it across the tank. They did this over and over. It was just like they were bouncing a ball!

Octopuses’ cleverness can pose problems for their caretakers. Sometimes, they find ways to escape from labs or aquariums! Octopuses are full of surprises. But that makes them fun to work with, says Amodio. Plus, there’s a lot left to discover about these animals. “We hardly know anything about them,” says Mather.