Mammoths are not still alive; they have been extinct for approximately four millennia. Video that emerged in early 2012 purportedly showing a woolly mammoth crossing a river in Russia was quickly shown to be a hoax.
The extremely blurry footage was supposedly taken by a nameless government-employed engineer in a remote area of Siberia. It seems to show a bear crossing the river with a large fish in its mouth, or a computer-generated mammoth image that has been intentionally blurred. The video footage seems to have been taken from a legitimate documentary by Ludovic Petho about his grandfather's escape from a Siberian prisoner of war camp and altered to show the alleged mammoth.