I recently reclaimed a fortress that got wiped out by a goblin ambush, and everything is going well except that there are a bunch of Yaks and Buffalo that belonged to the previous tenants are now roaming throughout my fortress that I can't select for a Pasture, nor do they show up for butchering, nor do they show up in my stocks menu.
I've tried setting cage traps for them, but they just walk right over the traps without being caught.
How do I go about catching these animals?
EDIT: I just realized that the Yaks belonged to a group of merchants who showed up just before the ambush, BUT still, how do I capture them?