Mostly crepuscular and nocturnal, some diurnal activity. More nocturnal in hot weather, more diurnal in cold weather. Boars usually were solitary, or in small male groups, except to breed or to feed on a clumped food resource. Breeding is promiscuous. Estrus occurs every 21 days once females reach sexual maturity, at about 6 mo.
Boars display and fight in the presence of estrous sows.
Increased reproduction in years of large acorn crop, or other food abundance. Reproductive rate can be increased significantly by access to irrigated pastures and other crops. May be a rangeland and agricultural pest in some areas. Humboldt Co. A major adverse impact on native wildlife is competition for mast crop, particularly for acorns in oak woodlands of California. In years of acorn shortage, when competition is most likely to occur, may compete with wild turkeys, mule deer, squirrels, black bears, and other species.