Table 1.

Behavioral categories and definitions (Bolhuis et al., 2005)

Behavior	Definition
State behavior
Active behavior
Standing	Bodyweight supported by four legs and pig remaining still
Walking	The pig’s legs move back and forth in a slow, rhythmic, symmetrical motion
Lying
Lateral lying	Lying with all the members extended laterally in one side
Ventral lying	Lying with the belly facing the ground with all the limbs under the body
Event behavior
Playing behavior	Jumping and turning around, running fast at a short distance, and suddenly lie down; focus animal close to pen mate, sniffing and lightly rooting; puts its front legs on the pen mates’ front body or its back
Tail-wagging	Moving the tail to the left or right when walking or standing
Exploring behavior	Sniffing or nosing the floor; biting or rooting the pen or through
Manipulative behavior	Rubbing belly of a pen mate with up and down movements of the snout; nibbling, sucking, or chewing an ear or the tail of a pen mate
Aggressive behavior	Ramming or pushing pen mate with head, with biting; mutual pushing or ramming or lifting pen mate