Boars are one of the passive animals found in the wild. They will ignore you but when threatened, they will counterattack for as long as the threat lasts until they are close to dying and then they will run from you when hit.
After killing a Boar, it's corpse can be skinned with a knife to get loot.
Before a Boar in the wild can be captured, it must first be injured enough that it will run away, instead of retaliating, when being attacked. It can then be captured with a Boar lariat and tamed by feeding it 3??. It will take multiple successful feedings to tame it.
A Boar mount can be stored Stables for safe keeping.