Squid not only swim, they fly! They don't just leap like dolphins, mind you. They actually accelerate through the air like rockets, by forcefully squirting water out of their bodies.
"It turns out that when these animals are flying, they move about five times as fast as they ever do when they're swimming," cephalopod expert Ronald O'Dor of Dalhousie University in Halifax, Canada, told Discovery News.
That superior aerodynamic efficiency suggests that these cephalopods may have developed flight not only for evading predators (as flying fish do) but also for saving energy during migration, O'Dor says. He and Julia Stewart of Stanford University presented their findings at the 2012 Ocean Sciences meeting in Salt Lake City, Utah, this week.
Tourists on a cruise ship off the coast of Brazil captured the first photographic evidence of the flying squid phenomenon back in 2010. But this study marks the first time anyone has analyzed the photos and compared the results to what biologists already know about swimming squid, which is D'Odor's expertise.
Each of 17 remarkable tourist photos of Sthenoteuthis pteropus (the species pictured in the illustration above) clearly show the trail of water behind each airborne squid:
"Because the photos were taken in continuous mode, we knew exactly what the interval was between each one," O'Dor says. "So we were able to measure directly the speeds of these animals and how they got launched."
The biologists then compared those results to their previous measurements of swim velocity and acceleration of two other squid species, Dosidicus gigas and Loligo opalescens. That's how they determined that air travel consumes far less energy than traveling by sea.
But if squid really prefer flight, wouldn't fisherman know about it?
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Not necessarily, O'Dor says. Years of keeping squid in the laboratory taught him that squid are prone to flying out of their tanks, but they are far less likely to do so if the lights are turned up. His suspicion is that most of the flying takes place at night.
To find out, O'Dor wants to track flying squid in the wild. Even animals as small as 50 grams can carry vitamin pill-sized electronic tags that ping ultrasonically; biologists are already using this technique to monitor the behavior and physiology of cephalopods and many other animals around the world.
"If we put accelerometer tags on these squid, we could measure how much time these squid spend in flight as opposed to swimming," he explains.
A 1912 illustration of Sthenoteuthis pteropus, by G. Pfeffer (Public domain via Tree of Life Web Project)
Flying S. pteropus photographed off the coast of Brazil (Photo courtesy Bob Hulse)