Wednesday, February 29, 2012

Nature Study Shows Squid Travel Faster in Air

There's a new study featured on Nature News which suggests that squid can travel up to five times faster in air than in water.

FYI: A squid propels itself by shooting water out of its siphon at high speed in the opposite direction to the direction of motion, just like a jet engine. In fact, this natural jet propulsion mechanism is what inspired the design of the jet engine!

Ronald O'Dor (a marine biologist from Dalhousie) and Julia Stewart (from Stanford) took a look at some rapid-succession photographs of what they think are orange-back squid (Sthenoteuthis pteropus) soaring through the air. Using the known time intervals between each photo, they calculated the squids' velocity and compared it to known values of squid propelling themselves through water.

This "flying" behaviour has been observed in squids for quite some time now, although not very often. It's widely believed that breaching is a predator-evasion tactic. However, based upon his new findings, O'Dor has suggested that squid may propel themselves through the air in order to save energy during lengthy migrations.

Some Questions

If it really is an energy-reducing measure for long distance travel, why don't we see squid leaping out of the water constantly, instead of the odd jump witnessed once in a blue moon?

Also, this study shows that squid can move faster through air than through water, but it doesn't address the logistics of propelling oneself out of the water. How much energy does it really take to break the surface? And is it worth the added speed of air travel during migration?

Finally, if squid really do jump out of water a lot more than we had previously thought, wouldn't this behaviour significantly increase their chance of predation by sea birds? (I do think this is probably true, but I also suspect predation pressure by birds is less than that of other things in the ocean, so the trade-off might be worth it).

O'Dor has proposed to investigate the proportion of time squid spend in air and in water by tracking them with tags that measure acceleration. This will give us clues as to how important flying behaviour is to the squid's lifestyle.


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