Legend of the Wyakin by David G. Rasmussen

A poetic prologue introduces the indigenous people's belief in animal spirit guides; called in the language of the Nez Perce tribe, "Wyakin." The prologue continues to introduce Cortez Modrables and the great wyakin: El Oso. A surreal but terrifying encounter inspirer the story of a Jewish immigrant family from Spain and the son, "Cortez." It's 1865 in the Upper Missouri River Montana wilderness. Cholera ravages the river boat The Modrables family is the unjust victim of this dread disease leaving the thirteen-year-old boy abandoned. He acquires the friendship of El Oso, a great grizzly bear and names it: Modrables El Oso. A Nez Perce boy, on a spirit quest, finds him and the boys become as brothers. The Nez Perce hunting band adopts the white boy, Cortez, foretelling his future into the Wyakin Trilogies.