Humboldt squid are large carnivorous molluscs (cephalapods) that can reach an overall length of 3.6 m (11.8 ft) and weigh as much as 90 kg (200 lb) (Norman 2002). The specimens that have been found in B.C. waters have been much smaller averaging 1.2 m (4 ft) overall length and 5.6 kg (12.3 lb) in weight (data courtesy Royal British Columbia Museum). Humboldt squid are open ocean animals that are constantly swimming. They travel in large groups of a similar age class. The mantle (tubular portion of the body) is long (up to 60 cm [24 in]) and the mantle wall muscle is up to 5 cm [2 in] thick. In this species, the mantle (body) makes up 40% of the animal's mass.The squid have two diamond-shaped fins attached to the mantle which they use to swim and glide. The head contains the very large eyes, the brain and a powerful and sharp parrot-like beak that is designed to cut through flesh. (Kurth et al. 2009). Attached to the head are 8 arms and two tentacles. On the outer edges of arms R2 and L2 are keel-like growths that provide stability for the squid when it is moving rapidly through the water. The tentacles can be rapidly extended to two or three times the length of the arms. Each arm has numerous, relatively weak, suckers on small stalks. Each sucker has a toothed chitonous rim that will dig into the flesh of prey. The suckers are able to rotate so that the toothed sucker rim comes in full contact with the prey. The ends of the tentacles have two diamond-shaped pads that have very large sucker rims and more robust suckers for grasping prey. Humboldt squid skin colour varies from deep purplish-red to white, and, like other cephalopods, muscle-bound chromatophores on the skin allow them to flash a range of colors (Smithsonian 2010). The chromatophores allow the squid to change colour in fractions of a second and there is some evidence that the squid communicate with each other via colour patterns and the frequency of display.