Javier Carrascosa

When the current dragged the giant squid toward a Spanish beach in October 2016, the creature was already near death. Wounded and suffocating, she stayed alive in the shallows—far from the deep, frigid ocean she came from—long enough for a tourist to snap some photos. Then she died and washed ashore.

Realizing he’d seen something unusual, the tourist, Javier Onicol, called up the president of a conservation nonprofit, who immediately called the marine ecologist Ángel Guerra. “It was incredible to me,” says Guerra, who outlined this chain of communication. Roughly one giant squid (Architeuthis dux) washes up dead in northern Spain each year, but none had ever been glimpsed alive outside of Japanese waters. Any live sightings of these cephalopods are vanishingly rare.

Even in death, the squid was an opportunity for scientists. Guerra rushed to the beach on the Bares peninsula, where he found the carcass, the size of a large adult man, still “very fresh.” He and his colleagues at the Instituto de Investigaciones Marinas, part of the Spanish National Research Council, set out to learn how the squid had met her end.

What they ultimately found added new detail to the hazy life story of giant squid. These elusive animals, it seems, sometimes turn pirate.

A few days after the squid washed ashore, Guerra donned a smock and rubber boots and cut into its carcass. She was an immature female weighing in at 105 kilograms, or 231 pounds. Her mantle—the part that’s not the arms—measured 122 centimeters, or 4 feet. (In Spanish, the giant squid is calamar gigante.) On the table, her limbs resembled a tangled heap of fresh sausage.

Guerra looked for clues to what had killed the squid. Her body was free of parasites, which sometimes kill marine animals. But she had a long, deep gash in the right side of her mantle. Squid have eight arms and two longer tentacles; both of her tentacles had been severed at the base. And her skin was gouged and spotted with the outlines of suckers. The sucker marks suggested a battle with another large cephalopod.

There are only two squid species in the area big enough to fight a giant squid. One is the neon flying squid. But its suckers don’t match the shape of the Bares squid’s wounds. The other is the Dana octopus squid. But this species has hooks instead of suckers. That meant the Bares squid’s attacker must have been a fellow giant squid. Based on the diameter of the sucker scars, the attacker was substantially larger—between 150 and 170 kilograms, Guerra says. This also means the attacker was another female, since male giant squid are much smaller.

The scientists considered what might have motivated the fight. The two giant squid probably weren’t fighting over a mate, since the victim was immature and had never mated. Cannibalism was also unlikely, since the attacker hadn’t taken any bites out of her. The most likely motive, the researchers decided, was kleptoparasitism—that is, food piracy. A bigger squid had attacked the victim to steal her food.

The wounded squid in the port on Spain’s Bares peninsula (Javier Onicol)

Off of northern Spain, giant squid often feed on schools of fish called blue whiting. The schools swim 400 meters or less below the surface, while the squid prefer to hang out around a mile deep. The squid must ascend to hunt, probably seizing fish from below with their tentacles, then descend again. In this scenario, a squid could save energy by pirating food from its neighbor rather than hunting its own fish, Guerra says: If the target squid has already carried its prey back to the depths to eat, the pirate could save itself a trip up to the shallow water. Staying below would also protect a pirate from predators such as dolphins and sperm whales that hang around the fish schools.

If a pirate happened to kill its victim, it would also reduce competition. The scientists think that’s what happened with the Bares squid: Its tentacles were ripped off in the fight over food. “The victim, disoriented and wounded, could enter a warmer mass of water in which the efficiency of their blood decreases markedly,” the authors write in a recent paper in the journal Ecology. “In this way, the victim, almost asphyxiated, would be at the mercy of the marine currents, being dragged toward the coast.” That’s where the Bares squid, in her last minutes, met the tourist.

Heather Judkins, a biologist at the University of South Florida at St. Petersburg, who studies cephalopods and wasn’t involved in the recent paper, says that this explanation makes sense. Although scientists know very little about how giant squid hunt—or do anything else—the papers’ authors “make a solid case” for piracy, she says. “Findings of these squid are very rare, so each animal documented helps build the story of the species.”

This story is still full of questions. No one knows how long giant squid really live, Guerra points out. We don’t know how male and female giant squid find each other in the dark, wide ocean, or how they mate. We don’t know how or where they lay eggs, where baby squid grow up, how adults migrate through the ocean. We don’t even know if giant squid make sounds.

Discovering things about Architeuthis dux has been “like a hobby” outside of Guerra’s main research in marine ecology and fisheries, he says. Giant squid appear so rarely that it’s almost impossible to study them. Earlier in his career, Guerra spent two 15-day research cruises trying unsuccessfully to film the animals. Now, as an emeritus professor, he has been able to add a little more to our understanding of these animals. “I am very happy with that,” he says.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.