Over the past few days, hundreds of carnivorous Humboldt squids have washed up on the shores of several Northern California towns, especially near Santa Cruz. The squid are a large (3-5 foot long), highly intelligent species native to Baja California and South American seas. Usually, they inhabit only the deep waters off the coasts. But sometimes when they enter a new region, these squids strand themselves on beaches by the hundreds. And scientists only have guesses when it comes to why.

Stanford squid researcher Hannah Rosen told the San Francisco Chronicle that the squid have been showing up in the Monterey Bay area of Northern California, as well as farther north, for over a decade. It's possible that climate change or El Niño conditions have driven them north, to seek cooler waters. She said that mass strandings of the kind people have witnessed recently have been seen before in the animals' usual habitats near Chile — as well as in California and farther north. It's possible that the creatures became disoriented in unfamiliar territory, and beached themselves while hunting.

Humboldt squid are very aggressive, and will eat pretty much anything smaller than they are. They have been known to approach divers, grabbing and touching them out of curiosity — there are no reports of humans being bitten or attacked. Humboldt squid also use chromatophores — special color-changing cells in the layers of their skin — to communicate with each other. They often strobe rapidly between red and white when meeting other squid.

Currently, researchers are testing the some of the squid found on the beaches to find out of they've ingested any neurotoxins from red algae blooms. If they have, this could be disorienting the animals and driving them ashore.

Rosen noted that Humboldt squid are impossible to keep in captivity because they will hurl themselves against the glass barriers in their cages until they kill themselves. Because they live in the deep ocean, scientists speculate that they are unused to barriers of any kind. This could also make it hard for them to recognize when they have come too close to shore. Because there are so many of the squids swarming off the coast of California right now, it's possible we'll see more mass strandings in weeks to come.

Read more via the San Francisco Chronicle, or read a scientific paper from the California Cooperative Oceanic Fisheries Investigations[PDF] on previous sightings and strandings of these squid in Northern California and Oregon.