Hunting the giant squid
In a world where mayhem is passe, not many items pique the curiosity of the satiated consumer. One that may apparently still do so is the giant squid. Reports of the local recovery of a large specimen recently have generated a wave of media interest worldwide.
Wildlife documentaries regularly disclose the courtship rituals of chimpanzees, social proclivities of porcupines, the fertilization of corals. But there is nary a one on giant squids for the simple reason that even in this age of the information superhighway, little is known about them. Probably not a single healthy live specimen has ever been seen by a scientist.
Apart from the fact that they live in the sea, nothing is known of the world they inhabit. Are they creatures of the deep? Most probably. But do they patrol the seabed or swim in the middle depths? Despite all the deep water fishing with huge nets that goes on these days—especially around New Zealand—giant squid are almost never captured.
Most of the few that are found turn up moribund and damaged on the coast, usually in mid to high latitudes.
The largest specimen on record anywhere was a 20-metre individual washed up on Lyall Bay, Wellington, in 1880. Over the last century, a smattering of specimens have been recorded from southern Japan, Great Britain, Scandinavia, Iceland and the east coast of North America. Earliest records (1639-1790) came from Iceland, where one was said to have had a beak so large that it filled a cart.
More reliable are reports of several specimens from around Newfoundland late last century. On one occasion, fishermen in a small boat investigated some floating wreckage. The “wreckage” bit at the gunwale and threw a tentacle over the boat. While grown men panicked, a 12-year-old boy had the presence of mind to hack the tentacle off. Not long after, another giant squid was stranded ashore. This one was described as alive and thrashing, and ploughed a 10-metre-long furrow in the beach with the jet of water from its siphon.
A tutor at a Norwegian Fishery College reported that a giant squid arched out of the water and pursued a row boat in one of the fiords, while in the mid-Atlantic a ship’s captain claimed to have clocked a giant squid at 20-25 knots.
Then, as we all know, had it not been for the bravery of Ned Land, a giant squid would have done for the nefarious Captain Nemo and his Nautilus in Jules Verne’s 20,000 Leagues Under the Sea.
Giant squids are the largest invertebrates known. They are cephalopods (a type of mollusc), kin with octopus and cuttlefish, and cousins of toheroa, snails and chitons.
The animal can be divided into three sections: the arms, head and the streamlined body proper. Eight thick muscular arms—each three or more metres long and attaining a circumference of 50 cm around the base—surround the mouth, together with two much longer tentacles. Although very slender, these are muscular and, near their distal end, expand into a pad that is lined with toothed suckers. The rest of the long tentacles are smooth.
Each arm also bears two rows of suckers. Suckers attain a maximum diameter of five or six centimetres, and each is on a mobile small stalk, and surrounded by a ring of serrated chitin (the horny material that covers crabs and adult insects). The two long tentacles are used like a pair of tweezers for seizing prey and conveying it to the mouth.
A formidable beak of chitin—not unlike a parrot’s beak, but able to be protruded and rotated by blocks of surrounding muscle—chops the prey into bite-sized pieces. Unlike the cart-sized beak of Icelandic legend, mandibles longer than 15 centimetres have not been encountered on any squid that has been measured.
Like gastropod snails, giant squids possess a radula—a tongue-like ribbon that bears transverse rows of small rasping teeth. Although the giant squid’s radula is small in comparison with the size of the body, it is huge (100 mm by 10 mm) compared with that of other molluscs. Food passes down the oesophagus into the stomach where digestion occurs.
The body of the squid is enclosed in an envelope termed the mantle. Water is drawn through the mantle cavity to aerate the large gills, then expelled forcefully through a narrow funnel to provide jet propulsion. This funnel can be turned in any direction to give considerable manoeuvrability.
Some oceanic squids are capable of high-speed swimming, but the musculature of giant squids is poorly developed in comparison, casting considerable doubt on the 25 knots alluded to earlier.
Noteworthy along with the tentacles are the eyes of the giant squid. At 25 centimetres in diameter, they are as big as volleyballs, and are the largest eyes in the animal kingdom.
Sexes are separate, and the males (seen much less frequently than females), can be distinguished by having two arms modified to assist with fertilisation. They are also much smaller than females. Females produce very large numbers of small eggs; males produce dozens of 20 cm tubes packed with sperm, themselves stored in a special cannister a metre long within the mantle cavity.
Cephalopods are notorious for their ink, and giant squid are well endowed here, too, with a large sac of gooey black ink ready for release through the siphon. The ink leaves a shape that may resemble the squid hanging in the water to confuse a possible predator.
What creature could pose a threat to such a formidable creature? One that has a fondness for squid of all types, including giants, is the sperm whale. The soft bodies of squid are quickly digested by the whale, but the chitinous beaks remain. Indeed, it is to protect against their sharpness that the sperm whale produces the sought-after tarlike ambergris in its gut.
The stomachs of sperm whales have been found to contain, on average, 2000 cephalopod beaks, and up to 8000 have been recorded. Amazingly, 2000 beaks are considered to represent only a couple of days’ sustenance for an average whale, and it is estimated that the ocean’s one to two million sperm whales annually consume 100 million tonnes of squid. (For comparison, the total world catch of fish is 70 million tonnes each year).
Beaks from most species of squid are distinctive, enabling a reasonable identification of the animal it came from. Most of the squid eaten by whales are smallish (0.6-8.0 kg, depending on the area), but some are giant squid. On a numeric basis, they are insignificant, but on a weight basis they contribute substantially to the diet of sperm whales in some parts of the world, especially in the Tasman Sea and in the eastern Atlantic off the Mediterranean Sea.
The heads of sperm whales are generally scarred by the serrated suckers of giant squids, evidence of battles in the deep. Some of these sucker marks are much larger than the 5-6 cm maximum diameter for squid suckers, leading to speculation about truly gigantic squids. In fact, the size of the scars is accounted for by whale growth—the scars enlarge as the whale grows, so big scars are simply relics of meals that fought back when the whale was smaller.
What giant squid themselves feed on is less certain. Guesses—and they are mostly that, for few of the specimens found have ever had anything in their stomachs—include fish and smaller species of squid.
Deciding how many species of giant squid exist has proved problematic. The few specimens that have been recovered differ from each other in confusing ways, and there has been a tendency to make almost every specimen a new species. Biologists are now favouring the idea that there are just a few variable species, all belonging to one genus, Architeuthis . Preservation causes considerable shrinkage and distortion, and exchanging specimens to facilitate comparisons—standard procedure for most taxonomists—is well-nigh impossible for those who study these creatures.
Some 18 specimens of giant squid have turned up in New Zealand waters over the last dozen years. The first—and most difficult to explain—was a large immature female that was found wedged in the filtering screens of the cooling water intake of the New Plymouth power station, and distant from any deep water. The second specimen was captured by a Japanese trawler from 500 metres of water around the Auckland Islands, and appeared to be a different species from the first specimen. A third specimen was brought to the Ministry of Agriculture and Fisheries in Wellington on the back of a ute by a rock lobster fisherman who had recovered it near the Castlepoint lighthouse. He had thought it was a large floating plastic bag, and was mystified why gulls were attacking it. Many features of this individual were intermediate between the first two specimens.
Most subsequent specimens have proved to be immature females, and the taxonomic picture remains obscure, but leaning towards fewer species.
Plans are afoot to bring a submersible to New Zealand in the summer of 1996/1997 to search for giant squid. National Geographic Television, the Smithsonian Institution, and our National Institute for Water and Atmospheric Research are considering a joint expedition, perhaps in Cook Strait or at Kaikoura. Since sperm whales are major predators on giant squids, expedition leader Clive Roper of the Smithsonian is interested in using the whales “as beagle hounds,” to lead the team to their quarry, since humans don’t have a clue as to where squid might be found.
Given the popularity of squid rings in seafood smorgasbords, would discovering the habitat of giant squid give rise to a new abyssal gastronomy? Probably not. Three scientists once cooked up a slice of Architeuthis to celebrate completion of a doctorate and found it permeated by the foul taste of ammonia. Apparently, giant squid produce ammonia because it is slightly less dense than water, and so imparts buoyancy.
With giant squid, big may be bitter, not better.