Board Thread:Speculation House/@comment-25045079-20140815193846/@comment-4010415-20140817122147

Vedran is right. It seems like the older, stronger grimm are bigger and have more bony spikes and plates. Hell, in The Emerald Forest, one of the Beowolves in the pack that attacked Weiss was bigger than the other Beowolves! That was our first look at an older, stronger version of a grimm, not the Ursa Major in Forever Fall Pt 2.

My headcanon is that the Beowolves in the Red Trailer were extremely young and thus hadn't yet grown their bony spikes and plates. They attacked Ruby because they had confidence in their strength in numbers, much like real wolves. They didn't expect her to pull out a sniper scythe and utterly slaughter them all.

Plus, Ruby was able to cut loose and just wildly and haphazardly swing her scythe around and fire off bullets everywhere. In The Emerald Forest, Weiss was there, and Ruby clearly showed that she's not used to paying attention to where someone else is and what they're doing on the battlefield. After running from the forest fire, Ruby said "I'm just fine on my own!" She is. If Weiss hadn't been there, Ruby would've been free to be more careless and haphazard with her strikes. Instead, she had to worry about causing collateral damage to a teammate, something that causes her to have to exercise self-control. She can't just go berserk on everything anymore.