Rontu is the former pet of the Aleutian hunters. "He was a much larger dog than any of ours," Karana tells us, "which besides have short hair and brown eyes. I was sure that he was an Aleut dog" (15.3). Rontu used to belong to the Aleut. His is also the leader of the wild dog pack that kills Karana's brother, Ramo. Though she swears she'll kill him, Rontu eventually becomes Karana's friend and constant companion. He's a symbol of the power of forgiveness.
Even though he is a dog, we put him in this section because he's treated as one of the primary characters. Karana also tames his son, which shows the power of these kinds of friendships.
At the end of Chapter 8, Karana vows revenge against the dog pack for killing her brother (8.50). We see that she manages to shoot Rontu in the chest in Chapter 15. But we also see that when it comes time to kill the dog, she can't bring herself to do it. She doesn't even know why she can't: "Why I did not send the arrow I cannot say" (15.22).
Instead, Karana brings him back to her house and nurses him back to health. This shows that for Karana, more violence is not the answer. She decides to tame and heal the dog. Rontu is changed from the enemy into a friend. She calls him "Rontu, which means in our language Fox Eyes" (15.37).