Table 1.
Ethogram used to score the behaviors of pigs in an ascending and descending gondola into a well filled with atmospheric air on days 1 and 2 and 80 or 95% carbon dioxide (CO2) on days 3 and 4.
| Behavior (event) | Description |
|---|---|
| Sniffing | Sniffing while lifting the head and considered a first sign of the pig becoming aware of the CO2 |
| Retreat attempts | Pigs backing away (18) |
| Gasping | A very deep breath through a wide open mouth that may involve stretching of the neck (25) |
| Escape attempts | Pigs running across the gondola and/or raising their forelegs on the side wall of the gondola (7) |
| Jumping | Jumping in air or against the wall of the gondola |
| Lateral head movements | Head movements to the side while convulsive expulsion of air from the lungs through the nose and mouth (26) |
| Muscular contractions | Defined as a period of struggling ranging from fairly vigorous running and movements to clonic convulsive seizures (18) |
| Loss of posture | The pig is in a recumbent position with total loss of control of posture |
| Behavior (state) | Description |
| Standing | The pig is in an upright position, without moving, with all four paws on the floor |
| Walking | The pig moves in a forward direction |
| Sitting | The pig is in a sitting position |
| Lying | The pig is in a recumbent position, still having (partially) control of posture (it may lift the head) |