Parameters analysed during trials in two tasks (fish and no fish) for the two harbour porpoises, Eigil and Freja, as well as for Freja blindfolded(Freja bf)
| . | Fish . | . | . | No fish . | . | . | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Parameter . | Eigil . | Freja . | Freja bf . | Eigil . | Freja . | Freja bf . | ||||
| Mean time per trial (s) | 6.0±0.6 | 5.6±0.8 | 12.2±2.0 | 5.8±1.0 | 4.5±0.7 | 9.9±0.6 | ||||
| Mean distance per trial (m) | 22.8±0.8 | 25.2±1.7 | 25.4±0.6 | 23.8±1.4 | 21.5±2.1 | 24.3±1.0 | ||||
| Mean number of clicks recorded per trial | 339.4±44.8 | 328.2±119.5 | 630.8±64.4 | 89.0±12.8 | 71.2±14.7 | 195.0±12.0 | ||||
| Mean distance to fish at transition point (m) | 4.4±2.6 | 1.9±0.8 | 3.9±1.7 | n.a. | n.a. | n.a. | ||||
| Mean click interval at transition point (ms) | 57.5±14.4 | 48.3±16.0 | 41.5±14.4 | n.a. | n.a. | n.a. | ||||
| Minimum click interval in near stage (ms) | 1.4±0.2 | 1.6±0.1 | 1.6±0.1 | n.a. | n.a. | n.a. | ||||
| Mean click interval in far stage (ms)* | 47.0±6.3 | 54.7±4.8 | 47.1±4.0 | n.a. | n.a. | n.a. | ||||
| Mean lag timeF in far stage (ms)* | 34.8±5.0 | 42.8±4.8 | 35.0±3.0 | n.a. | n.a. | n.a. | ||||
| Mean lag timeR (ms)* | n.a. | n.a. | n.a. | 40.2±2.8 | 34.8±1.7 | 31.7±0.7 | ||||
| Mean click density (clicks m–1)* (excl. near stage) | 4.1±1.0 | 3.2±0.2 | 7.4±0.7 | 2.7±0.2 | 3.1±0.3 | 6.2±0.8 | ||||
| Mean speed (m s–1) | 5.4±0.5 | 5.9±0.5 | 3.0±0.4 | 6.3±0.4 | 5.9±0.5 | 3.3±0.4 | ||||
| Slope (±95% CI) (ms m–1) before splash for DR≤26 m | 0.23±1.45 | 2.34±1.59 | 0.96±0.63 | – | – | – | ||||
| Slope (±95% CI) (ms m–1) after splash* | –0.50±0.96 | –0.17±0.93 | 0.02±0.94 | 1.80±0.37 | 1.41±0.55 | 1.71±0.90 | ||||
| Slope (±95% CI) (ms m–1) for DF(far stage)* | 0.19±1.24 | –0.03±0.62 | 0.59±0.76 | n.a. | n.a. | n.a. | ||||
| Slope (±95% CI) (ms m–1) for DF(near stage) | 10.91±3.90 | – | 9.72±7.15 | n.a. | n.a. | n.a. | ||||
| . | Fish . | . | . | No fish . | . | . | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Parameter . | Eigil . | Freja . | Freja bf . | Eigil . | Freja . | Freja bf . | ||||
| Mean time per trial (s) | 6.0±0.6 | 5.6±0.8 | 12.2±2.0 | 5.8±1.0 | 4.5±0.7 | 9.9±0.6 | ||||
| Mean distance per trial (m) | 22.8±0.8 | 25.2±1.7 | 25.4±0.6 | 23.8±1.4 | 21.5±2.1 | 24.3±1.0 | ||||
| Mean number of clicks recorded per trial | 339.4±44.8 | 328.2±119.5 | 630.8±64.4 | 89.0±12.8 | 71.2±14.7 | 195.0±12.0 | ||||
| Mean distance to fish at transition point (m) | 4.4±2.6 | 1.9±0.8 | 3.9±1.7 | n.a. | n.a. | n.a. | ||||
| Mean click interval at transition point (ms) | 57.5±14.4 | 48.3±16.0 | 41.5±14.4 | n.a. | n.a. | n.a. | ||||
| Minimum click interval in near stage (ms) | 1.4±0.2 | 1.6±0.1 | 1.6±0.1 | n.a. | n.a. | n.a. | ||||
| Mean click interval in far stage (ms)* | 47.0±6.3 | 54.7±4.8 | 47.1±4.0 | n.a. | n.a. | n.a. | ||||
| Mean lag timeF in far stage (ms)* | 34.8±5.0 | 42.8±4.8 | 35.0±3.0 | n.a. | n.a. | n.a. | ||||
| Mean lag timeR (ms)* | n.a. | n.a. | n.a. | 40.2±2.8 | 34.8±1.7 | 31.7±0.7 | ||||
| Mean click density (clicks m–1)* (excl. near stage) | 4.1±1.0 | 3.2±0.2 | 7.4±0.7 | 2.7±0.2 | 3.1±0.3 | 6.2±0.8 | ||||
| Mean speed (m s–1) | 5.4±0.5 | 5.9±0.5 | 3.0±0.4 | 6.3±0.4 | 5.9±0.5 | 3.3±0.4 | ||||
| Slope (±95% CI) (ms m–1) before splash for DR≤26 m | 0.23±1.45 | 2.34±1.59 | 0.96±0.63 | – | – | – | ||||
| Slope (±95% CI) (ms m–1) after splash* | –0.50±0.96 | –0.17±0.93 | 0.02±0.94 | 1.80±0.37 | 1.41±0.55 | 1.71±0.90 | ||||
| Slope (±95% CI) (ms m–1) for DF(far stage)* | 0.19±1.24 | –0.03±0.62 | 0.59±0.76 | n.a. | n.a. | n.a. | ||||
| Slope (±95% CI) (ms m–1) for DF(near stage) | 10.91±3.90 | – | 9.72±7.15 | n.a. | n.a. | n.a. | ||||
The duration of a trial was determined by the first and last click analysed from an echolocation sequence (see Materials and methods). The values for regression slopes (±95% confidence interval, CI) for mean click intervals are shown over distance to reference (DR; before splash DR<=26 m; after splash DR=18–12m excluding the near stage in fish), and over the distance to fish (DF) in the far stage as well as in the near stage. Regression slope values with a ±95% confidence range that include the value 1.3 are not significantly different from the slope of the two-way transit time. Those ranges including zeros do not show a significant regression, those excluding zero are slopes significantly different from zero. Significant positive regression slopes (marked in bold)show a positive correlation between click interval and distance to reference or distance to fish, respectively. The dashes indicate insufficient data. n.a., not applicable/not available. Number of trials included for Eigil/Freja/Freja bf are: fish=5/5/5, no fish=5/5/4. *Calculated for DR=18–12 m