If you just care about the group (and want the model to identify groups), then you’re probably safe just labeling each group. However, if you want to know how many objects are in a group, you need to label all of them individually.
My gut is that you’re going to need less data if you label them each individually because the underlying object is much more similar (a wolf looks a lot like any other wolf; a single wolf is quite different from a group of 4 wolves).