Fox families are very supportive of their cubs and you will generally see the adults nearby when cubs are out playing in the open. If you find a fox cub which is separated from its parents or is above ground with its eyes still closed, it could well need rescuing. Before you do though, watch from a distance if you can to see if he parents return. It may be that you disturbed them in the middle of a move, as parents do move their cubs between different earths from time to time. Obviously an injured cub may need rescuing anyway and look out for signs of dull eyes or droopy posture, for a cub which is constantly calling for parents but not getting a response or has respiratory problems.
Most people are only likely to be involved in a fox rescue where the animal is injured or trapped in some way. Road injuries are the most common and there are some handy dos and don’ts. Do be aware that foxes have seriously sharp teeth and claws. An injured frightened animal is likely to defend itself so do not try to handle the animal unless you have thick gloves or appropriate equipment. Call Wildlife A&E or your local animal rescue and wait for expert help. Droopy, drowsy looking foxes can be suffering from ticks, mange or toxic poisoning so may well need medical assistance. Bright and strong looking animals that just happen to have found their way into your shed or garage will, with the right encouragement and opportunity, run for it at the first opportunity and that is most often the best plan.