The Truku people believe that the utux, or ancestral spirit, brings blessings and misfortunes upon them based on their actions, hence their actions and speech follow the Gaya and ancestral custom in all aspects of everyday life. Many of the ceremonial festivities of the Truku are focused on the utux faith, mainly sowing, harvest, headhunting, utux worship, dedication, and healing rituals. The contents and processes of the rituals are closely integrated with the utux, and they also reflect different problems that the Truku people face with regard to their way of life in the mountain forest. Apart from the interaction with the utux through rituals, the Truku people also use oral traditions to pass down the necessary mindset and protocol when interacting with the utux.
Truku people experienced significant change in political and social norms in the modern era, and the rituals and oral traditions evolved accordingly. During the migration east to Hualien, many ritual ceremonies that were previously conducted by priestly families were taken up by familial patriarchs and influential individuals instead. Due to a ban on headhunting and tattooing by the Japanese government, the headhunting ritual is no longer held. The ritual of utux worship also became obsolete as the Japanese government scattered the Truku people to different locales and western missionaries critiqued the utux. Following the migration of the Truku people to the plains, the Japan government introduced rice agriculture. As rice became the primary crop of the Truku people and productivity increased, the rituals of the sowing and harvesting of the millet lost its function, and were no longer held. Healing rituals also became obsolete as the Truku people converted to western religion. Missionaries rejected the utux faith, leading to the gradual distancing of the Truku people from shamans and relevant rituals, though there are still a few shamans who can perform healing rituals. Dedicatory rituals are the relatively more developed tradition. Dedicatory rituals not only maintained the occasion of ritual, which is when the Gaya is offended or before hunting, but also entered into aspects of the Truku people’s modern lifestyle, such as acquisition of property, long distance travel, marriage and funeral. As for ritual related oral tradition, following the conversion of the Truku, elements of western religion entered into the repertoire of the Truku oral tradition. The Truku people’s stories begin to describe the utux as God, and their ancestral land as heaven and hell.
There is no indication that the Truku rituals and oral traditions mutually reinforced each other through interpretation, as both supported the utux belief in different ways. Due to their detached nature, the two traditions underwent different evolutionary change due to different causes as the Truku people adapted to tribal and social changes. In 1990s, as the Truku elites attempted to revive traditional rituals, similar phenomenon appeared as well. At the time the discussion concerning the interpretation of “traditional” rituals among the Truku elites were focused on the place of the utux in the rituals but did not attempt to reinforce ethnic uniqueness or tradition through the narration of historical events or oral traditions.