Property:Wildness
A number between 0 and 1, displayed as a percentage. It is used to determine the Minimum Handling Skill stat, and combines with the Tame Animal Chance and Train Animal Chance stats to determine the final tame/train chance.
Additionally, animals need over 10.1% wildness in order to be able to lose the tamed status. Pen animals are excluded, and will never become wild again (may still wander off map if left outside a pen).
Finally, the degradation interval of training/tamed status varies between 720,000 ticks (200 mins) and 360,000 ticks (100 mins), inversely related to the wildness stat. Dryads and pen animals are exceptions, and will never lose training nor tame status due to decay.
Do note that some events are also related with this property. For instance, the Farm Animals Wander In incident can only spawn animals with at most 35% wildness.