News/narrative register. 治療してもらった uses the benefactive ~てもらう 'have (someone) do X for one' in past form — the tiger is the beneficiary of having its injuries treated. 村人たちの手で 'by the hands of the villagers' is a formal way of marking the agent of a passive action, emphasizing the volunteers' active role. 帰される is the passive of 帰す 'to send back, cause to return' — 'was returned.' 保護区 'protected area, reserve' is conservation vocabulary.