The little octopus picks up two halves of a coconut shell and carries them across the ocean floor with her suckers. Suddenly, startled, she drops the shell halves and dives inside.
Like a lot of you, I watched that video and wondered, "Just how smart are cephalopods, anyway?"
Turns out, on a scale of one to chimpanzee, octopuses are probably somewhere close to matching wits with a dog. We don't really know for sure. It's difficult to devise intelligence testing for an animal that is so clearly different from us.
That said, research does offer some tantalizing hints that we may need to rethink our anti-invertebrate biases. Octopuses have personalities. They can recognize and respond to individual humans. And there's even some evidence that they play.
It makes sense that the octopus would be a smart animal, once you understand where and how it lives.
Octopuses are basically balls of delicious protein. And, unlike their cousins, the mollusks, they don't have protective shells. So they're fair game for just about anything with an appetite.
At the same time, octopuses are also solitary creatures—they generally live alone from the time they're born, and don't have others to rely on for protection or to teach them the ways of the world. Stupid octopuses, or even octopuses that aren't quick on the uptake, get eaten.
The other pressure on octopus intelligence is environment, said Jennifer Mather, Ph.D., a comparative psychologist at the University of Lethbridge in Alberta, Canada. Mather has spent her career studying cephalopod intelligence. She describes the near-shore tropical waters, where octopuses first evolved, as an ecosystem even more complex than the tropical rain forest.
"There's lots of opportunities for food, and lots of opportunities to become food," she said. "And the octopuses have to figure that entire, complex system out for themselves."
The result is a naturally inquisitive creature that makes individual decisions about how to use resources. Mather calls octopuses "specializing generalists" when it comes to diet, meaning that they can eat a lot of different things, but each individual tends to pick a very distinct diet of personal favorites.
These simple facts about octopus behavior are relatively easy to collect. That isn't true of all cephalopods. Squid, for instance, are much more difficult to study because they have a hair-trigger flight reflex that sends them careening into the walls of a tank anytime you so much as flip on a light, said James Wood, Ph.D., director of education at the Aquarium of the Pacific in Long Beach, California.
But this doesn't mean all octopus research is simple. Thornier questions—how octopuses learn, what their relative IQ is and whether they have anything we'd call consciousness—are very hard to pin down.
In these murky waters, everything is up for debate. One such subject: Tool use.
Neither Mather, nor Wood, was surprised to see an octopus using a coconut shell as a portable hidey-hole. But they both question whether it counts as tool use—and they question it for very different reasons.
Wood favors a conservative definition of tool use. By that standard—an animal using a solid object to solve an immediate problem, rather than just to provide defense against potential predators—there aren't any real clear examples of octopuses using tools. But, he said, defining tool use isn't a black or white issue. There's no single, official right answer.
Mather works from a different, but still valid, definition. She doesn't count the coconut shell as a tool, because the octopus isn't modifying the shell in any way, and isn't using it to alter other things in its environment.
But she does think octopuses use tools. In 1991, she documented octopuses collecting rocks and stacking them, outside the opening of a shelter, to form a protective fence. In fact, she said, the octopuses tended to do this before they went to sleep. That doesn't count as tool use to Wood, but with several scientifically sound definitions, there's room for interpretation.
Play is another hot topic. We think of play as silly time, but it's actually a sign of intelligence.
"You're making the thought transition from, 'what does this object do,' to, 'what can I do with this object'," Mather said.
Not everybody agrees octopuses play, but Mather thinks they do. She, and colleague Roland Anderson, Ph.D., set up a study where they put an octopus in tank and, periodically, gave it a plastic bottle. The first few times the bottle appeared, the octopus would examine it, and then cast it aside. But, sometimes, the octopus would try something different.
Two of the eight octopuses in the study eventually began a repetitive game. First, they moved to the far end of the tank, away from the outlet that brought in fresh water. Then, they used their natural ability to shoot water jets to push the bottle toward the outlet, where the flow of fresh water would bring it back. Push, back. Push, back.
"When one of them did it more than 20 times in a row, Roland called me and said, 'She's bouncing the ball!'," Mather said.
Oh, and that apocryphal story, about the octopus that breaks out of its tank at night, crosses the room, gets into a neighboring tank and proceeds to treat itself to a buffet dinner, before slinking back home before the aquarium keepers arrive in the morning? It's true.
"That's one of the urban myths that's for real. Stuff like that has happened lots of times," Wood said.
In fact, even in the wild it's not unusual to see octopuses pop up onto the land for short periods. They use the trick to escape predators and to hunt crabs in tidal pools.
"We ascribe stories like that to the octopus being sneaky, but that might be anthropomorphizing a bit," Wood said. "It just might be an octopus being an octopus."