Behavior and general characteristics
Humboldt Squid are carnivorous marine invertebrates that move in shoals of up to 1200 individuals. They swim at speeds of up to 24 kilometers per hour (15 mph/13 kn) propelled by water ejected through a hyponome (siphon) and by two diamond shaped fins. Their tentacles bear suckers lined with sharp teeth with which they grasp prey and drag it towards a large, sharp beak.
They are known to be very aggressive and attack divers who venture too close. There have been reports of these squid attacking divers and fishermen in the Sea of Cortez, sometimes trying to drag them deep into the water. In December of 2009, three divers were killed in the Sea of Cortez after they found themselves caught in the middle of a Humboldt Squid feeding frenzy. The scuba tanks of Nicholas Barbin and two other unnamed divers washed up on the shores of northern Mexico four days after their disappearance. Torn pieces of their wetsuits were found to be soaked in the ink discharged from the Humboldt Squid as a defensive measure. However, Roger Uzun, a veteran scuba diver and amateur underwater videographer who swam with a swarm of the animals for about 20 minutes, said they seemed to be more curious than aggressive. In circumstances where these animals are not feeding or being hunted, they exhibit curious and intelligent behavior.
The shallowest depths of Humboldt Squid's daytime habitat are only within reach of the extremes of saturation diving, so little is known of their daytime behavior. Humboldt Squid are thought to have a lifespan of only about one year, although some researchers believe they may survive up to four years. They may grow to 2 metres (7 ft) and weigh 45 kilograms (100 lb). They can rapidly change their skin color from deep purplish red to white using chromatophores (specialized skin cells) in what some researchers believe is a complex communication system. Experts have also stated that the squid hunt for their prey of small fish and krill in a cooperative fashion, which would be the first observation of such behavior in invertebrates. Humboldt Squid are known to hunt near the surface at night, taking advantage of the dark to use their keen vision to feed on more plentiful prey.
Recent research suggests that Humboldt squid are only aggressive while feeding. At other times, they are quite passive. Their behavior while feeding often extends to cannibalism and they have been seen to readily attack injured or vulnerable squid of their own shoal. This behavior may account for a large proportion of their rapid growth.
The Humboldt squid lives at depths of 660 to 2,300 feet in the eastern Pacific, ranging from Tierra del Fuego north to California. It gets its name from the Humboldt Current in which it lives off the coast of South America. Recently, the squid have been appearing further north, as far as Alaska.
Generally, the tube (or body) constitutes about 40% of the animal's mass, the fin (or wing) about 12%, the tentacles about 14%, the outer skin about 3%, the head (including eyes and beak) about 5%, with the balance (26%) made up of the inner organs.
They often approach prey quickly with all ten appendages extended forward in a cone-like shape. Upon reaching striking distance, they will open their eight swimming and grasping arms, and extend two long tentacles covered in sharp 'teeth,' grabbing their prey and pulling it back towards a parrot-like beak, which can easily cause dramatic lacerations to human flesh. The whole process takes place in seconds.
Recent footage of shoals of these animals demonstrates a tendency to meet unfamiliar objects aggressively. Having risen to depths of 130–200 metres (430–660 ft) below the surface to feed (up from their typical 700 metre (2,300 ft) diving depth, beyond the range of human diving), they have attacked deep-sea cameras and rendered them inoperable. Reports of recreational scuba divers being attacked by Humboldt Squid have been confirmed. One particular diver, Scott Cassell, who has spent much of his career videotaping this species, has developed body armor to protect against attacks. Each of the squid's suckers is ringed with sharp teeth, and the beak itself can tear flesh, although it's believed they lack the jaw strength to crack heavy bone.
The Humboldt Squid feeds primarily on small fish, crustaceans, cephalopods, and copepod. The squid uses its barbed tentacle suckers to grab its prey and slices and tears the victim's flesh with its beak and radula. The Humboldt squid is also known to quickly devour larger prey when cooperatively hunting in groups.
Commercially, this species has been caught to serve the European community market (mainly Spain, Italy and France), Russia, China, Japan, South East Asian and increasingly North and South American markets.
The squid are fished at night, when it is easier to lure them with lights used by fishermen that make the plankton the squid feed on shine, which causes the squid to rise to the surface to feed. Since the 1990s, the most important areas for landings of Humboldt Squid are northern Peru and Mexico.
There are numerous accounts of the squid attacking fishermen and divers in the area and attacks on humans are regularly seen, but only when they are being fished. Their colouring and aggressive reputation has earned them the nickname diablos rojos (red devils) from fishermen off the coast of Mexico as they flash red and white when struggling with the fishermen.
Humboldt Squid and El Niño
Although Humboldt Squid are generally found in the warm Pacific waters off of the Mexican coast, recent years have shown an increase in northern migration. The large 1997-98 El Niño event triggered the first sightings of Humboldt Squid in Monterey Bay. Then, during the minor El Niño event of 2002, Humboldt Squid returned to Monterey Bay in higher numbers and have been seen there year-round since then. Similar trends have been shown off the coasts of Washington, Oregon, and even Alaska, although there are no year-round Humboldt Squid populations in these locations. It has been suggested that this change in migration is due to warming waters during El Niño events, but other factors, such as a decrease in upper trophic level predators that would compete with Humboldt Squid for food, could be impacting the migration shift as well.
Humboldt Squid and ocean acidification
A study published in Proceedings of the National Academy of Sciences found that by the end of this century ocean acidification will lower the Humboldt squid's metabolic rate by 31% and activity levels by 45%. This will lead the squid to have to retreat to shallower waters where it can uptake oxygen at higher levels.
- ^ Sea of Cortez, 1995
- ^ Jumbo squid invade San Diego shores, spook divers, Associated Press, July 16, 2009
- ^ Behold the Humboldt Squid | Outside Online
- ^ Behold the Humboldt squid. Tim Zimmermann, Outside Magazine, July 2006.
- ^ a b The Curious Case of the Cannibal Squid, Michael Tennesen, National Wildlife Magazine, Dec/Jan 2005, vol. 43 no. 1.
- ^ Squid Sensitivity Discover Magazine April, 2003
- ^ DeeperBlue.net - Fanatical About FreeDiving, Scuba Diving, Spearfishing & Technical Diving
- ^ Cassell, S. Dancing with Demons. Deeper Blue, 2005-12-15
- ^ a b Zeidberg, L. & B.H. Robinson 2007. Invasive range expansion by the Humboldt Squid, Dosidicus gigas, in the eastern North Pacific. PNAS 104(31): 12948–12950.
- ^ Rosa, Rui, and Brad A. Seibel. (2008) Synergistic effects of climate-related variables suggest future physiological impairment in a top oceanic predator. PNAS 105: 20776-0780