Identifying hyenas by their spots can be a difficult task. Hyenas make this task even more difficult by "sacking out" in mud holes, which leaves them essentially spotless. I don't mean spotless as in clean, certainly they are not that type of spotless. By spotless I mean almost none of their spots are actually visible.
In addition to using spot patterns to identify the hyenas, there are various other tactics we use to identify hyenas. One of the first ways I learned to identify individual hyenas was by their ears. Many hyenas have notches in their ear from squabbling over food, play that got a bit too rough, or aggressive interactions with other hyenas or lions. Recognizing ear notches is very useful when only the head of the animal is visible or the entire hyena is covered in mud. Ear notch identification is not much use at night or when the animal is running. I have found a combination of facial features, such as ears, and spot patterns to be most effective. Relying soley on one or the other just doesn't cut it.
The pictures below shows why just knowing spots does not always work. If you look closely at the left ear, you can see this guy's ears are in rough shape, with multiple notches in the ear. This Kyoto, an immigrant male in the Talek West clan. If you look closer and have an imagination you may see shades of William Wallace, ready to lead his army to victory against the English (see Braveheart for those of you that don't get this bit)!