Corrected entry: When Big Wig explains what happened when he lead the fox away from the rest and they heard a cry of pain, he says something about being just about to stop limping. Problem is, Hazel is the one with the injured leg, not Big Wig. In the book Big Wig does fake a limp to trick the fox, but since he's not seen doing so in the film the comment makes no sense whatsoever.
Corrected entry: At the very start of the film, Fiver comes across footsteps and a smoking cigarette butt. If the smell of the recently departed man wasn't enough to keep him away from that spot (and Hazel, peacefully grazing a few feet away), then the very smelly cigarette smoke should have done the trick.