Board Thread:Speculation House/@comment-14138255-20141024002244/@comment-24994749-20141025004911

Or Oobleck really meant it when he mentioned dogs were actually good conpanions for hunters. Being the father and the uncle huntsmen, and even the mother having been a huntress it's not strange to think the family pet would receive some sort of training if it wasn't downright the job-sidekick of one of them for missions. Particularly when you remember that Yang's flashback implied that, in Patch, Grimm infested areas are at walking distance from the residential ones.

Actually, maybe Taiyang got Zwei as a guardian dog after the beowolves incident with Yang and Ruby when they were little.