For red deer Spring is the scruffy season. If you see one of them the chances are that its coat is full of darker patches where the old fluffy winter warming layer is coming away or is being pulled out by the animal itself. It's also worth looking closely at the heads of the younger animals in the mixed herds. Some of these are less than a year old and detecting whether they are male or female is quite easy - but only if you can get close enough.
The male has the bumps (burrs), while the females' heads are mostly flat.