In this conceptual system vacuum activities could be considered autochthonous behaviors. This type of behavior occurs relatively often in swine housed in close confinement, particularly farrowing or gestation crates, or on concrete floors without bedding material and with a concentrated diet. Bar biting is considered to be an indicator of boredom, but since its occurrence is increased prior to farrowing, it also may be a component of vacuum nest building or a displacement activity linked to predelivery discomfort. Also see Cribbing. A natural group of horses consisting generally of a stallion, several mares, and several sexually immature individuals of various ages.
Bared teeth is a threat signal and is an integral part of aggressive biting.
The amplitude of a bark is highest at the beginning of the sound and falls sharply thereafter. The pitch is usually between 2 and 3 kHz. Barks appear to be both threat and alarm calls, having a high arousal effect on other pigs, particularly preweaned young. Other animals react to barking with quick orientation, followed by a brief period of immobility and silence. Behavioral symptoms are difficult breathing, repeated barking sounds, and uncoordinated locomotion.