Table 2.
Characteristics of the different types of approach and associated behaviours.
| Measured variables | Behavioural unit definitions |
|---|---|
| Distance (minimum distance between the orca and the diving guide reached during a given approach) | The orca approaches the diver from: |
| - Very close (less than 5 meters) | |
| - Close (between 5 and 20 meters) | |
| - Far (more than 20 meters). | |
| Angle of approach | The orca approaches the diver from: |
| - The front: | |
| * from the right side of the diver (angle: 30 to 120°) | |
| * from the left side of the diver (angle: 200 to 330°) | |
| * facing the diver (angle: 0°) | |
| - Below: | |
| * moving just under the diver | |
| * arriving vertically from deep water | |
| - The back. | |
| Swimming speed | - Slow: the orca moves but the movements of its caudal fin are hardly detectable |
| - Fast: at least one caudal fin movement per second. | |
| Gaze laterality | The orca looks at the diver with: |
| - its right eye | |
| - its left eye | |
| - both eyes (bilateral) | |
| For a given approach, the eye used may change during the behavioural sequence and each gaze change is counted for the laterality analysis. | |
| Gaze duration (mono- and binocular pooled) | The orca looks at the diver for: |
| - less than 6 seconds (Short gaze) | |
| - more than 6 seconds (Long gaze) | |
| For a given approach, we measured the total gazing duration. | |
| Head movements | - Horizontal (the orca turns slightly its head towards the diver) |
| - Vertical (the orca is facing the diver and moves the head up and down several times in a row). | |
| Whistle calls | - Whistling (a high-pitched modulated frequency is heard) |
| - Silence (no species-specific sound is heard) | |
| It is not possible to confirm whether the caller is the observed orca or a neighbouring one. | |
| Belly presentation | The orca moves the head up presenting its belly to the humans. |
| Body rotation | The orca rotates its body along the horizontal axis. |