Hrm... I'll give that a shot. I'm a little more leery of war elephants now though - during transport to the zoo one "tamed" elephant broke free and went on a rampage. He killed two (more) dwarves before my archers were forced to put him down - as a "pet" he no longer tripped cage traps, so recapture was not an option. I shudder at the thought of what an elephant with twice the muscle can do before an archer is lucky enough to peg him in the throat.
Incidentally, I stumbled upon an easy way to acquire large amounts of elephants to train. Use channels to make a comb or sawtooth pattern through territory elephants regularly traverse, and set it up so the only dry route to one side of the comb passes through a tunnel dug into the mountain. When elephants encounter the comb, they'll most likely want to move from one side to the other, which because of poor pathing funnels them into the mountainside and your waiting cage traps.
Question: is there an "empty cage" command I'm missing somewhere? Because elephant training involves feeding them, I've got four cages that are now useless because of plump helmet seeds left in the bottom. And with 4-6 elephants charging headlong into my base every couple of minutes, I need them.