In traditional management, animals ranged freely in sparse oak forest (dehesa in Spain, montado in Portugal), they are constantly moving around and therefore burn more calories than confined pigs. This, in turn, produces the fine bones typical of this kind of jamón ibérico. At least a hectare of healthy dehesa is needed to raise a single pig, and since the trees may be several hundred years old, the prospects for reforesting lost dehesa are slim at best. True dehesa is a richly diverse habitat with four different types of oak that are crucial in the production of prime-quality ham. The bulk of the acorn harvest comes from the holm oak (Quercus rotundifolia) from November to February, but the season would be too short without the earlier harvests of Pyrenean oak (Quercus pyrenaica) and Portuguese or gall oak (Quercus lusitanica), and the late cork oak (Quercus suber) season, which between them extend the acorn-production period from September almost to April. See also Presunto List of pig breeds References Pig breeds originating in Spain Pig breeds originating in Portugal