The gold rush brought tens of thousands of miners and settlers to northern California, putting pressure on native populations. Gold mining polluted the water and killed fish. Deer left the area. The settlers brought new infectious diseases such as smallpox and measles. The northern Yana group became extinct while the central and southern groups (who later became part of Redding Rancheria) and Yahi populations dropped dramatically. Searching for food, they came into conflict with settlers, who set bounties of 50 cents per scalp and 5 dollars per head on the natives. In 1865, the settlers attacked the Yahi while they were still asleep.