Orphaned (Ape Quartet #4) - Eliot Schrefer - Bog

Snub is a young female gorilla, somewhat jealous because her mother is occupied with a new baby, curious of the world around her, a world that is being reshaped by shaking ground and mountains that bleed fire, and most terrifyingly by a new form of predator that walks on two legs; when her mother is killed Snub finds herself in charge of her baby brother--and accompanied by one of the not-gorillas, a very young female who has been orphaned by the violence of her own kind.