So my last fortress "Angerhorn" was experiencing a common catsplosion just as any healthy mid-game fort, kittens were being ordered to be butchered all the time and the adoption messages were constant. FPS was rapidly falling.
But at the same time I completed my power plant, which was basically a deep hole dug in the middle of a river that then linked to a horisontal tunnel powering my water wheels.
A short time after the plant had been running, an unexpected message popped to my screen.
"[Name], kitten has died after colliding with an object" After a short inspection, I determined that the kitten had leaped down the artificial waterfall and it's guts were currently being mangled by my water wheels.
These messages would pop out every now and then while my cat population slowly started to plummet. After some time spent watching the river I noticed that cats and kittens, stray or not, would every once in a while go down the stairs leading to the riverbed (They were used back when the river was frozen to excavate the top of my waterfall). These stairs were only one tile away from the "+"-shaped drain and the water depth near them would rapidly change between 0 and 4. I dont know why the cats would wander there alone as the place was nowhere near any of my assets. Maybe they tried to fish the abundant trout inhabiting the stream or perhaps the dried part of the river was a good place for verming hunting? Nevertheless the felines would be caught in the strong current and be flushed down the drain.
I regard this a truly patriotic deed from the cats involved: Not only were they giving up their lives for the common good but decided to do so at my power plant so their blood could run the mills used to feed the population!
This also never resulted in any tantrums, as suicidal behavior was pretty random and even the worst catdwarves would only lose a single pet every once in a while, letting their bad thoughts cool down.
I think I still have the save somewhere, so I can post screenshots if you want them.
Here is the rough layout of the water intake area as I remember it.
###~~~~~###
###~~_~~###
###~___~<##
###~~_~~###
###~.~,.###
###.,.,.###
# earth wall
, exposed riverbed
~ water
_ hole
< stairs up