Sunday, May 9, 2010

Colossal Squid: study suggests its not the aggressive monster of myth

There is so little that we know about the deepest recesses of the oceans. Our ignorance and our fears often unleash our imagination to conjure up the worst of monsters - not just in today's sci-fi movies, but for centuries man has felt that there are unspeakable horrors lurking in the ocean's blackness.

As many of my readers know, in March I was on assignment for National Geographic to film the jumbo squid, or Humboldt squid, in Baja, Mexico. Working with Scott Cassell of the Undersea Voyager Project, who has spent many years encountering and studying the jumbo squid, this was my first opportunity to meet these voracious predators on their home turf. I soon learned these are very aggressive animals that will attack just about anything if they think it means a potential catch.

There are actually three large species of squid - each with a name that one-ups it's smaller cousin. The jumbo squid, followed by the rarely seen giant squid, and topped by the even rarer colossal squid. Each squid is considered a powerful and aggressive predator based on what evidence was available on any of the species combined with anecdotal evidence such as bite markings on large whales, like sperm whales who, as one of the larger squids' natural enemies, are suspected of diving deep and hunting large squid using echo-location.

It is now being suggested in a recent scientific study, that the colossal squid, the rarest of the rare and the world's largest invertebrate, may not be as aggressive as our imaginations lead us to think. Reported in the BBC's Earth News, the study by Dr. Riu Rosa of the University of Lisbon and Dr. Brad Seibel of the University of Rhode Island suggests that the colossal squid just may turn out to be a slow moving, lies-in-wait ambush predator. This theory is based on metabolism studies of related squid species and then extrapolating those findings to account for the colossal squid's size, in addition to other factors, such as the cold temperatures in which the squid lives.

"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.

Studies of trace isotopes in tissues samples from the few dead specimens of colossal squid that have been found, show evidence of one of the squid's primary food sources: the arctic toothfish. Based on that, the study determined that an 11-pound (5 kg) toothfish could nourish a 1000-pound (500kg) colossal squid for up to 200 days. It all makes reasonable sense. Given that the deep depths contains less large scale bio mass than in shallower, sunlight-bathed waters; a large predator would need to maximize its use of whatever it could catch, and a lower metabolism - which can equate into less activity - would be one way to accomplish that.

Nonetheless, based on the few specimens that have been examined, the colossal squid is a formidable source of nightmares and mythological legends. It can reach a length of possibly 50-feet (15m) from the tip of its large mantle to the end of its tentacles, equal in length to that of a sperm whale. And whereas the jumbo and giant squid have small teeth that ring each sucker disk on its arms and tentacles, the colossal squid has large, swiveling hooks to latch on to their prey. Yikes!

We know so little about the ocean depths. It has been said that we have more data about the backside of the moon than we do about the oceans depths that make up the vast water volume of our blue planet. The more we commit ourselves to studying it, the more we will learn what is happening to our fragile marine ecosystems and what we should do to protect them. And along the way, a few nightmares might get dispelled, a few legends might get rewritten.

All the same, I'll sleep with the light on tonight.

Read the complete article in the BBC Earth News.

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