80% of rolling occurs in a spot where another equine has rolled and part of its function may be to include the opportunity to deposit scent over the body.
Males especially smell chosen sites before and after rolling.
Rolling could also be linked to grooming and scratching hard to reach areas.
Often rolling occurs at the end of a period of recumbency when they are lying down, they often roll before they get up.
Rolling can account for up to 13% of self grooming in equines.
Rolling most likely has three possible causes, one is definately for scratching on those difficult to reach places, especially during the loss of the coat in the Spring and Summer months, this could be link to pleasure of scratching iches and to the skin conditions that might occur on the donkey. Also, it is related to scent marking, donkeys will paw the ground, not to remove the grass but to generally stir up any scent or odour they have been able to smell before deciding to roll on the ground. It is often thought to be laying down the scent over the the scent of other donkeys.
And finally it can be related to skin conditions such as lice, mites and also can be a sign of collic in severe cases. The way to identify the difference is, is that normal rolling is slow and steady and it happens occassionally, whereas rolling which is related to colic or pain or irritation of the skin would happen much more frequently and in a much more vigorous way. I think it is pretty important that we perhaps get that across just in case there are any confusions and people think their donkey is pawing and rolling because it is just wanting to have a scratch when actually it might be a sign of colic.
If you have any questions please don't hesitate to ask.