Giant Humboldt squid, which can grow as big as a man, speak to each other in flashes of color, their whole bodies quickly changing from red to white and back again. But just what they’re communicating has long been a mystery to scientists.

Now, new video analysis is allowing marine biologists to begin cracking this jumbo squid’s code.

The new research is the first to track communications between free-swimming Humboldt squid, partly because the animals show no fear of human divers. They’ve been known to rip off a diver’s mask and to attack lighting and camera equipment. The predators sport suckers lined with sharp teeth, have a two-inch-long beak used to sever the spines of fish, and have no qualms about ripping apart and eating injured comrades.

Scientists mounted cameras on three of the animals—a first for squid research—and are using the footage to begin deciphering the chatter of flashes and flickers used by these five- to six-foot-long (1.5- to 1.8-meter) “red devils.” The new study is published Wednesday in the Journal of Experimental Biology.

Lost in Translation

One of the Humboldt squid’s more “attention-grabbing behaviors” is rapidly flashing nearly its entire body from red to white to red again, says Hannah Rosen, a doctoral student at Stanford’s Hopkins Marine Station in Pacific Grove, California. Actual light, like bioluminescence, isn’t involved.

It’s probably an attempt to communicate, she says, based on National Geographic Crittercam video first taken in 2009 that shows most squid flash only in the presence of other squid. (See “Jumbo Squid Flash, Flail in First Ever Squid-cam Video.”)

The animals can speed up or slow down their flashes to send different messages. But researchers have no idea what the squid are trying to say—maybe they’re broadcasting come-ons to prospective mates, or throwing down with potential rivals. “That is the question of the hour,” says Rosen, the lead study author.

When Humboldt squid want to go incognito, they start to flicker like a computer screen on its last legs. The animals use special skin cells to produce waves of red and white that scroll across their body. Most likely, the predators are trying to match the undulating pattern of sunlight filtering through the water, says Rosen, “like light reflecting on the bottom of a swimming pool.”

Humboldt squid range from the coast of Chile to as far north as Alaska. They spend much of their lives in the mid-water region, far from the bottom. If they need to blend in with their surroundings using camouflage, they can’t match their skin color and texture to nearby rocks or algae, like octopuses can, Rosen explains. Instead, the squid mimic the pattern of sunlight across their body to confuse potential predators.

Squid in Swimsuits

The researchers acknowledge that they’ve been able to study only two animals so far. But they plan to outfit more Humboldt squid with video cameras to get a better handle on squid behavior.

And they will literally be outfitting these predators. The only way Kyler Abernathy, director of research for remote imaging at National Geographic, and the Crittercam team could mount cameras on the soft-bodied animals was to attach their equipment to a tube made of Lycra-like material that slipped over the main part of the squid.

The squid “sweaters”—cut from child-size swim shirts—left the animals’ fins, arms, and tentacles free so the red devils could move unhindered.

Humboldt squid are the first squishy invertebrates that the Crittercam team has outfitted, Abernathy says, which is partly what drew him to the project. “This is a really different animal than we’ve ever worked with.”

He’d like to modify his design so that both the camera and sleeve detach from the squid. Currently, only the camera floats free after a release is triggered. The animals are then left sporting children’s swimwear.

So hopefully in future deployments, the sleeve and camera come off, and predators known for terrorizing divers aren’t left in wacky outfits. (See “Photos: Humboldt Squid Have a Bad Day at the Beach.”)