An entire episode was shot in Australia, in a caravan park .... yes ..... the whole park was booked, filled with crew and Mr Grylls of course. All the 'food' placements was marked with markers, routes were plotted, etc.
Yes, he does the stunts himself.
If he makes a mistake or the scene is not done correctly the 'action part' was re-shot !!!!
Regular breaks were taken during the shooting and after a days 'work' they retire to their caravans.
and that's 'how it's made'