That conclusion was reached by studying the physiology and feeding habits of other deep sea species and scaling up to the colossal squid's huge size.

Rarely seen alive or dead, the elusive ocean giant is thought to reach up to 15m long. Little is known about its way of life but the colossal squid (Mesonychoteuthis hamiltoni) is thought to roam in the deep waters of the Southern Ocean.

The kraken
Its large size and predatory nature fuelled the ancient myth of the underwater "Kraken" seamonster (which will familiar to moviegoers following the Pirates of the Caribbean sequel) and modern speculation that the colossal squid must be aggressive and fast, attributes that allow it to prey on fish and even give sperm whales a hard time.

"The understanding of the mode of life of the colossal squid is a significant event in the ongoing investigation of enigmatic large animals of the ocean," says Dr Rui Rosa from the University of Lisbon in Portugal, who undertook the study with Dr Brad Seibel from the University of Rhode Island, Kingston, US.

Counting calories
In a recently published study in the Journal of the Marine Biological Association of the United Kingdom, the reserachers present the first estimates of the metabolic and energetic demands of this cold-water deep-sea giant.

The researchers calculations reveal the colossal squid survives on only a small amount of prey.

"Our findings demonstrate that the colossal squid has a daily energy consumption 300-fold to 600-fold lower than those of other similar-sized top predators of the Southern Ocean, such as baleen and toothed whales," says Dr Rosa.

It is thought the cold temperature in which the squid lives affects its metabolic rate.

"The colossal squid is not a voracious predator capable of high-speed predator-prey interactions," says Dr Rosa. "It is rather, an ambush or sit-and-float predator that uses the hooks on its arms and tentacles to ensnare prey that unwittingly approach."

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