The picture below shows a scene with a bear attacking Leonardo DiCaprio, who is playing Hugh Glass in the movie ' The Revenant'. How was the scene shot? Was the bear real?
Industrial Light and Magic were responsible for creating the CGI bear. Yeah, it's CGI and not in-fact a real bear. They used reference footage from actual bears, even including a bear attack filmed at a zoo where a drunken man stumbled into the sanctuary. They used a stunt man to literally throw Leo around and tear at him. This meant that painting out the stunt man would have taken an incredible amount of skill and time. Then all they'd have to do is put the CGI bear in. As you can tell, visual effects has come a long way. I wondered myself how they did this before looking up some of the visual effects techniques used. Props to ILM for their great work.
Here are some references for the above information. You'll find interesting comments on these links.
You can find the project on ILM's website (ilm.com) however there isn't much information on there yet. They usually wait a while before posing VFX breakdown videos, if at all.
A Variety article, which gives some insight into the shooting methods and conditions that they filmed in. Also, confirming that the bear is CGI and that "Inarritu had studied bear attacks on YouTube"
Indiewire article, which is rather more in-depth and talks about the technical aspects such as fur simulation, Maya for animation, and using RenderMan for rendering.