Tribal religions in India
Roughly 8.6 percent of India's population is made up of "Scheduled Tribes" (STs), traditional tribal communities. In India, those who are not Christians, Muslims, Jews or Zoroastrians are identified as Hindus—the reason being that varied beliefs and practices are allowed in Hinduism, and it is accorded as a geographical identity rather than merely a religious one.
Source: Wikipedia — Tribal religions in India (CC BY-SA 4.0)