。
Wild beasts live in the forest.
Literal
Wild-beast [topic-は] forest [in-に] is-living-[ている].
野獣 ('wild beast, savage animal') has an archaic/dramatic flavor, distinct from the neutral 野生動物 ('wild animal'). It carries connotations of ferocity and danger. 住んでいる is the stative ~ている form describing ongoing habitation.