In my current fortress I have built a simple butchery tower. Wildlife crossing the map gets caught in traps, and then released into special, species-specific rooms without taming. The 1*4 rooms each feature a hole and a hatch cover. On the pulling of a lever, the hatch opens and a quarter of that room's livestock falls eight z-levels to a messy death. The bits can then be butchered straight away. Don't use bridges instead of hatches, because mammoths and other large modded creatures won't fall through them. Much quicker than slaughtering tame animals, because you can just regulate numbers with a simple lever pull. All automatic.
So far, pretty standard stuff.
But, I have greatly increased the range of biomes that all the critters wander in, with the intention of my dwarves tasting every possible meat. Gotta catch em all.
And the problem is, a few years in, the wildlife has stopped coming. I have just five wild species in rooms in my tower. Presumably, the game is waiting for them to path off the map before generating any new creatures on the edges.
The only solution I can think of is, start again, with all the MAXAGEs set to 1000, and then wait for ages until I've caged every single possible animal before releasing them from their cages into the tower. (Since afaik animals still come in if you have caged wildlife, just not if you have things roaming around)
However, I leave the problem to more powerful minds than mine. Is there any way I can actually stock my tower with roaming creatures whilst still catching more animals from the map edge? And without messing with the life expectancies and starting again?