I just embarked to a nice lake with a volcano in the background and my two "free" pack animals were both yak cows. I hate yaks. They starve rather quickly so I usually just butcher them on the spot anyhoo, but feeling a bit dwarfier than usual, I decided to kill them with style.
My first method was to drop them from the cliffside into the lake. I watched them fall & get stunned from hitting the lake bottom, but they weren't drwoning and just swam out of the lake moments later. Next, I dropped them off the cliffside to the meadow a good 7 z-levels below, thinking this will surely kill or injure them. It didn't. So I dropped them with their four broken legs back into the lake. They still lived. So now I thought to drop a whole floor several z-levels into the lake with the yaks on it, but they STILL survived!
The final trial of the yaks was dropping them straight into the volcano (a true dwarf would have probably done this from the start) so I dropped them from a whopping 18 z-levels above the surface of the lava. I waited several seconds thinking, "I didn't drop them from THAT high, they should have splashed by now..." and then I get the message "You have struck almandine!" "You have struck cobaltite!" etc. so I zoomed to my lovely yaks, realizing they had made it halfway through the volcano with no injuries from either lava or magma crab, awestruck, I watched them descend deeper into the volcano, discovering things deep underground for my dwarves. When I found the long overdue, dying yaks, I couldn't believe it! They had made it all the way to semi-molten rock before they even started to acquire injuries!
Can anyone explain what/why this happened?