Table 2.
Characteristics of adult Risso's dolphin (Grampus griseus) spin and non-spin foraging dives. Values represent mean (±s.d.) per dive, and GLMM test results for significance of difference between spin and non-spin dives and bouts. MSA: minimum specific acceleration (m s−2; mean for 5 s pre- and 5 s post-dive-onset). IDI: inter-dive-interval.
| foraging (F+) |
GLMM results |
||||
|---|---|---|---|---|---|
| non-spin (S−) | spin (S+) | estimate (s.e.) | t | p | |
| dive time (min) | 6.4 (1.6) | 9.6 (2.1) | 3.0 (0.4) | 7.8 | <0.0001 |
| maximum depth (m) | 177.8 (76) | 425.7 (132) | 265.0 (20.9) | 12.7 | <0.0001 |
| descent speed (m s−1) | 1.98 (0.4) | 2.47 (0.5) | 0.7 (0.1) | 7.0 | <0.0001 |
| ascent speed (m s−1) | 2.18 (0.4) | 2.30 (0.4) | 0.3 (0.1) | 3.9 | 0.0001 |
| descent angle (degrees) | −41.4 (16.5) | −59.9 (13.5) | −18.4 (3.1) | −6.0 | <0.0001 |
| ascent angle (degrees) | 46.5 (16.1) | 68.6 (11.0) | 23.1 (2.8) | 8.3 | <0.0001 |
| mean pre-MSA (m s−2) | 0.64 (0.17) | 1.99 (0.97) | 1.0 (0.1) | 8.2 | <0.0001 |
| mean post-MSA (m s−2) | 0.80 (0.21) | 1.00 (0.55). | 0.1 (0.1) | 1.9 | 0.06 |
| IDI (min) | 10.0 (4.8) | 14.7 (3.6) | 4.8 (0.9) | 5.6 | 0.0002 |
| no. buzz | 5.5 (3.5) | 10.7 (7.9) | 5.4 (1.2) | 4.4 | 0.0001 |
| depth start clicking (m) | 15.5 (9.7) | 90.2 (76.5) | 92.1 (10.8) | 8.6 | <0.0001 |
| time to start clicking (s) | 7.7 (3.9) | 35.6 (26.6) | 31.3 (3.7) | 8.3 | <0.0001 |
| foraging time in dive (%) | 42 (23) | 49 (16) | 7.3 (3.2) | 2.3 | 0.03 |
| buzz depth (m) | 148.1 (56.7) | 344.2 (122.9) | 196.8 (18.1) | 10.8 | <0.0001 |
| depth first buzz (m) | 126.1 (55.5) | 287.0 (129.6) | 154.3 (20.5) | 7.5 | <0.0001 |
| time to first buzz (s) | 120.5 (71.6) | 144.8 (60.9) | 23.5 (11.5) | 2.1 | 0.053 |
| inter-buzz-interval (s) | 45.8 (45.5) | 49.8 (40.9) | 4.0 (7.3) | 0.5 | 0.59 |
| buzz rate bout (min−1) | 0.7 (0.2) | 0.9 (0.6) | 0.3 (0.2) | 1.4 | 0.17 |