All the pigs in the Forest are owned by Commoners. Each year they are allowed onto open forest land for 60 days, known as pannage season, to eat acorns which would otherwise poison the ponies.

Pannage always lasts 60 days but the start date varies according to the weather - and when the acorns fall.

The Forest Verderers decide when pannage will start. The right to allow pigs out onto the Forest in this way is called the 'right of mast' and is not held by all commoners.

At other times the pigs must be taken in and kept on the owner's own land, with one exception. Pregnant pigs, known as "privileged sows" are always allowed out.