Both. They mostly keep in packs but the male pack leaders will solo hundreds of miles and come back to the pack. A pack will comb a whole mountain side solo, so just because you thought you saw a solo wolf doesn't necessarily mean the pack wasn't near. I saw a black one feeding on a road kill and as I drove towards it, the wolf ran in the bush and after I drove by I looked in my review mirror and it had came back to the kill.

Bobby