In Gladiator , Ridley Scott insisted on having a scene where the circus tigers attack Russell Crowe.
This memorable sequence required a huge amount of preparation and work, while the shots where the tigers appear in action are ultimately very brief.
“Initially, we were going to use trained tigers,” says Neil Corbould, the special effects supervisor. “But when we were shown the trained tigers, we found them a little too wild to do everything with! So Ridley decided to have a fake tiger made for all the close-ups where Russell would have to interact with the animal.”
The fight with the tigers was ultimately achieved using three different special effects.
1-Every time we see a tiger approaching Maximus, it's a composite shot. The trainers simulated tiger attacks in front of a green screen, and these shots were then merged with those of Russell Crowe dodging the animal.
As in these shots (Russell Crowe and the tiger are not actually together):
2-When the tiger is on Maximus' shoulders and attacks him, it is not Russell Crowe, but a trainer.
You can actually see his face in this shot:
3-When Maximus is on the ground with the tiger on him, it is a fake tiger.
A skillful editing technique allows these three special effects to be merged to create a scene that is fluid and impressively realistic.