I really doubt black bears take too many deer or moose. Maybe if they were somehow injured they would be able to catch them, but I somehow doubt a 600 lbs bear would have much of a chance catching up with one.
Guess what they surely do!!! Here they have seen them take them down more than once. In the fall when they get them it is not uncommon for them to bury them in leaves. Then on a warm winters day come out of hybernation and have a lunch with them. Also here back about 14 years ago they tried to reintroduce the Woodland Caribou and the biggest killer of them was in fact bears. The project was dropped and it has been decided not to tryit ever againas it was a big waste of resources..