It was not until Tarni and Mack told them their story did Bai Lu suddenly realized one thing: if they didn't have the experience of living in a beast tribe, and there were only two of them living in the upper reach of that river, then why does Tarni know the beast language?
Since they met in the central plaza, Tarni has been fluently using the beast language to talk with them, sounding like she is an expert in the beast language. How could Tarni do that?