The presented picture shows 4 trophic levels of the ecosystem. The first level is made out of primary producers, plants. The second level is made out of herbivores that feed on the plants. The third level is made out of predators that eat herbivores. The fourth trophic level is made out carnivores that eat other carnivores. In our case, the only organism belonging to the fourth trophic level is the wolf.
One benefit of animals living in a group are that they can stand up to other animals more easily. One cost is that they have to share food and resources.