Invertebrates
Humboldt Squid
Dosidicus gigas · also called jumbo squid, jumbo flying squid, diablo rojo
The Humboldt squid is a metre-plus predator that lives about as long as a garden pea plant. It grows explosively, hunts in flickering red-and-white packs, spends its days in water that would suffocate almost anything else, spawns, and dies — all inside a year or two.
Overview
Dosidicus gigas lives in the eastern Pacific, along the Humboldt Current from Chile to Mexico and periodically far to the north. The mantle reaches 1.2–1.5 m and the animal up to 50 kg, grown from a hatchling in one to two years. It seizes prey with two long tentacles and bites it apart with a hard beak.
The red devil
Fishermen call it diablo rojo for the way it flushes deep red, then strobes red and white by firing skin pigment cells — possibly signalling to others while hunting in shoals of a thousand or more.
Living in dead water
By day it dives 200–700 m into the oxygen minimum zone, near-anoxic water, and drops its metabolism to idle. At night it rises to feed at the surface. It is also a frequent cannibal.
A volatile fishery
It supports one of the largest invertebrate fisheries on Earth (Peru, Chile, Mexico), with catches that swing wildly year to year, and a range that has surged north and then retreated since 2000.
Status
The Humboldt squid is Not Evaluated and abundant, but its wild swings in number and range, plus heavy fishing and a changing ocean, make its future hard to call.
Humboldt Squid: common questions
Are Humboldt squid dangerous to humans?
They have a fearsome reputation, fed by accounts of divers being bumped, grabbed, and dragged down, and by the sharp beak and toothed sucker rings that can tear skin and wetsuit. In feeding situations, especially around fishing boats where squid are excited and competing, they can be genuinely hazardous and divers there use protective gear and stay in cages or close to the boat. But researchers who have filmed undisturbed Humboldt squid describe wary animals that flash warning colours and keep their distance, and there are no confirmed human deaths. The danger is real but tied to context; a relaxed squid is not looking to attack a person.
How does the squid survive water with almost no oxygen?
The eastern Pacific has a thick layer of water, the oxygen minimum zone, where oxygen is far too low for most active animals. The Humboldt squid spends its days there, partly to avoid predators and the warm surface. It copes by strongly suppressing its metabolism, essentially idling, slowing its swimming and its oxygen demand until it rises again at night. Its blood pigment and gills are also efficient at extracting what little oxygen is present. This ability to use the oxygen minimum zone as a daytime refuge is thought to be one reason the species has done well, and there is concern that as these low-oxygen zones expand with ocean warming the squid's habitat may actually grow.
Why does the Humboldt squid's range keep changing?
Its numbers and distribution are unusually volatile. During and after strong El Nino events, and through the 2000s, Humboldt squid expanded far north of their usual range, appearing in large numbers off central California, Oregon, Washington, and even Alaska, and growing to larger sizes in some areas. After about 2015 the northern populations largely collapsed and the squid in the core range off Peru became smaller and matured earlier. The drivers are debated but include ocean temperature and food supply, the near-disappearance of large predators such as tuna, billfish, and sharks that once kept squid numbers down, and the squid's own boom-and-bust life cycle.
Is it true they eat each other?
Yes, cannibalism is common and well documented. Stomach contents of Humboldt squid regularly include other Humboldt squid, often smaller individuals, and this can make up a significant part of the diet, especially when other food is scarce or when many squid are packed together, such as around a fishing operation where hooked or injured squid are quickly set upon by the rest. It is one reason the group-hunting behaviour is hard to interpret; a shoal of Humboldt squid attacking a school of fish is also a shoal in which any squid that fumbles a catch or is hooked may become the next meal.