I never knew that exotic animals would never reproduce even if tamed. Never got a fort with a Dungeon Master in it before that bug in .31.xx prevented them, so if I wanted an exotic I'd go into the raws and change the tag to [PET] as a workaround.
Side note: While I did this with elephants and rhinos in my current fort (still 31.25 while I work out some concepts before moving on) as well as changing the grazer tag to something manageable for both, a word of caution: DON'T DO IT unless you keep only one female alive... apparently they both have offspring with the same frequency and at the same numbers as dogs. Also, since the babies still contain massive amounts of meat/bones/etc compared to most other butcherables, my 'cleanup' operation resulted in about 8k units of meat, enough bones to make 3.5k assorted bone bolts and nearly 100 bone crossbows, and I'm still trading solely on masterwork skull totems. All this from a panicked 2-year butchering spree.
Back on topic: so now if you catch a wild animal and 'tame' it, it has a chance to go feral on you again until you retame? I'm already beginning to rethink my plans to inhabit an area full of Giant (insert cat or badger subtype here) on the grounds of almost guaranteed maulings.