After yesterday's cliffhanger, I suppose I should explain what it means for a squid to fly. Can they control their aerial trajectory? Can they gain altitude, once airborne, which is the definition of "true" flight?

Strangely enough, very little research has been done on squid flying. Or maybe this isn't so strange--it's not the easiest behavior to study, after all! In my time at sea I've seen hundreds, maybe thousands, of flying fish, but I've never seen a flying squid. And yet ommastrephid "flying squid" live all over the place: Todarodes pacificus in the Western Pacific, Dosidicus gigas in the Eastern Pacific, Illex illecebrosus in the Atlantic, and Ommastrephes bartramii circumglobally, just to name a few. I suspect the two big reasons they're hard to spot are (1) their densities don't approach those of flying fish, and (2) they're nocturnal.

Occasionally, though, people do see them. In addition to the picture I posted in yesterday's comment thread, here's another one someone snapped. Both photos are probably Ommastrephes bartramii (the same obliging squid that showed off its eyelid for us).



But hey, guess what! I was totally wrong about ommastrephids being the only cephalopods that can fly (despite their exclusive access to the common name of "flying squid"). Check out this paper on flight in my favorite little reef squid, Sepioteuthis sepioidea.

Or, if you don't want to strain over the tiny print, enjoy these highlights:
Some researchers do not use the term 'fly', but prefer the term 'gliding'. In this paper, however, we will refer to this airborne jet propulsion as flight based on observations of squid posture and movement that suggest to us a more active behaviour than simple gliding. We report new observations of flying behavior in a species of squid (Sepioteuthis sepioidea) previously thought to be too heavy for long distance flight . . .

While airborne, both squid rapidly undulated their lateral fins . . . After approximately 4 s of flight, both squid rapidly flared their arms downward. This posture acted as an airbrake . . . The speed of the airborne squid closely matched that of the boat, which was approximately 9-10 m s-1.

Jetting by squid while underwater produces the initial force which propels the animal out of the water. Jetting of water while the squid is airborne has been observed on at least five occasions in at least two genera . . . the force generated by continued jetting of water while airborne produced acceleration . . . If applied at the proper angle, this force could produce lift and, ultimately, flight in squid.
[emphasis mine]