Why is this octopus trying to eat an inflated pufferfish?

A strange encounter between a pufferfish and an octopus has scientists wondering if the mighty octopus has finally met its match.

Watch: Rare footage shows an unusual encounter between an octopus and pufferfish in the Seychelles

The odd encounter has scientists guessing at the octopus's intentions.

Why is this octopus trying to eat an inflated pufferfish?

A strange encounter between a pufferfish and an octopus has scientists wondering if the mighty octopus has finally met its match.

Watch: Rare footage shows an unusual encounter between an octopus and pufferfish in the Seychelles

The odd encounter has scientists guessing at the octopus's intentions.

Octopuses are among the most sophisticated predators in the animal kingdom. The same cannot be said about the humble pufferfish. But a recent encounter between the two suggests the creatures may nonetheless be equally matched.

Earlier this month, divers Chris Taylor and Carrie Miller were exploring a coral reef off the coast of Fregate Island in the Seychelles when they came across a big blue octopus and a pufferfish locked in a stalemate.

The octopus had the puffer in its grasp and was attempting to drag it into a crevice in the coral. The divers watched as the octopus spent several minutes trying to pull the fish into its hole, but the fish never budged.

Then, perhaps realizing the fish was far too big to fit in the crevice, the octopus emerged from beneath the coral and enveloped the bloated, spiny puffer with its muscular arms. The two carried on like this for nearly 15 minutes, both refusing to yield.

Taylor and Miller had to surface before a victor could be crowned, so no one knows how this encounter ended—but scientists can speculate.

Proficient predator

Big blue octopuses, also known as day octopuses (a reference to their diurnal nature) are fully capable of taking down something their own size, says Roger Hanlon, senior scientist at the Marine Biological Laboratory in Woods Hole, Massachusetts.

“These animals can take on prey items as big as they are,” Hanlon says. “They can extend their arms and web to make the functional gape of their mouth enormous.”

Octopuses feed primarily on crabs, mussels, and other invertebrates, but they’ll occasionally go after reef fish and other cephalopods, according to Hanlon, who has authored two books on cephalopod behavior. (Watch as octopus eats jellyfish, then clings to it as likely weapon.)

Octopuses employ a unique hunting strategy when going after fast-moving prey. First, they latch onto their victim using the highly-sophisticated suckers that line the underside of their arms. Then, once they’ve got a good grip on it, they bring the prey towards their mouth where it can be hacked into bite-sized pieces by their parrot-like beak, and if necessary, injected with a paralyzing agent housed in the octopus's posterior salivary glands. (This battle between an octopus and a crab has a surprising twist.)

“There aren't many animals that eat that way,” Hanlon says. “It gives them the ability to eat small critters and really big ones.”

Decent defender

Although Hanlon believes the octopus in the video could have consumed the pufferfish, he wonders why it would want to. “It’s interesting that [the octopus] is willing to take on this very strange fish, which we know is poisonous,” Hanlon says.

Nearly all species of pufferfish harbor tetrodotoxin in their internal organs. This neurotoxin makes the fish taste foul to predators and is at least 1,200 times more potent than cyanide. A single pufferfish can contain enough tetrodotoxin to kill 30 adult humans, and there is no known antidote. Although tetrodotoxin is toxic to humans, no one knows how octopuses are affected by it. Hanlon suspects this octopus was either unaware of the danger or immune to the poison.

But even if the octopus was immune to the toxic innards of the fish, how could it possibly consume an animal covered in sharp spines?

According to Hanlon, spikes and spines offer little defense against octopuses. The boneless, muscular arms of an octopus are so soft and malleable, they can wrap around sharp edges without piercing their skin.

Still, it remains unclear why the octopus would go after such formidable prey—perhaps the reef had become devoid of bivalves and crustaceans.

Marine mystery

It’s anyone’s guess who came out on top, says Miller.

Similar footage of battles between pufferfish and octopuses have appeared online in recent years, all of which ended before a winner was crowned.

Until more research is done, we can only speculate how these rare and unusual encounters ended.

Diver Carrie Miller is author of National Geographic's 100 Dives of a Lifetime.
Annie Roth is a freelance science writer based in Santa Cruz, California, who has written for National Geographic, Inside Science, the San Jose Mercury News, among others. Follow her on Twitter.