I caught my bimac, Lefty, at low tide a couple of months ago. He's got about a 2 ˝” mantle. I know that octopuses can open muscles and clams by drilling a tiny hole near the hinge and injecting a toxin (tranquilizer?), but Lefty hasn’t done this yet. He has brute-forced very small muscles open, but given up on 2" long ones, so when I found a 3" diameter rock scallop (which have thick shells) while SCUBA diving, I expected it to easily be strong enough to keep Lefty out, at least until he gets larger. I was wrong. Lefty demonstrated a technique for killing a scallop that I had never suspected; he suffocated it. He opened his body like a 6" wide parachute and draped it over the scallop. When the scallop opened (about 3/4" max) and tried to draw water inside, the thin membrane of Lefty's body would seal against the edges of both halfs of the shell and just bow inward. The scallop couldn't get any new water, and after about 20 minutes, Lefty was crawling into the dead scallop. Lefty didn't use strength to hold the scallop closed, he just used his body like a plastic bag and denied oxygen to the scallop until it suffocated.
Lefty could only eat a small fraction of the scallop because it was so large, and I was impressed that he was able to use such an indirect, almost passive, technique to prevail where a direct approach would have failed. I suspect that this might be how they kill fish too.
I imagine that this is not an uncommon behavior, is it?
I think that this technique must be largely instinctual, since there was no trial and error or experimentation involved, Lefty just saw the big clam, enveloped it, and patiently suffocated it. I wish I could give Lefty credit for being so intelligent as to have reasoned out that this would work, and invented it on his own, but there's no way he's that smart (It took ME ten minutes just to realize what he was doing!). Instinct must have handed him this technique. What do you all think?
On the other hand, where was instinct when Lefty was unable to open little 2" long muscles? The suffocation trick might not work on muscles, which can "hold their breath" for hours between tides, but why didn't instinct tell him to drill a little hole in them with his radula and inject his tranquilizer? He just wrestled with them for a while and gave up. Will he have to deduce the drill a hole trick, on his own, or is he simply to small for that to be an option. I've saw a full grown bimac do it, so maybe size matters when it comes to radulas.