Table 1.
Summary of research vessel, recording device and amount of data analysed over 4 years of research between 2009 and 2013.
Figure 1.
Example spectrograms of all signature whistle types identified (n = 28) from common bottlenose dolphins in Namibia.
Frequency (kHz) is on the y-axis and ranges from 0 to 48 kHz. Time (s) is on the x-axis. The scaling is the same for all spectrograms. Spectrogram settings: FFT 512, Hanning window, overlap 50%. The numbers in the top right corner of each spectrogram are the unique SW identification numbers of each signature whistle type.
Table 2.
Data summary showing the frequency of occurrence of each signature whistle type and the whistle loop structure.
Figure 2.
Spectrograms of signature whistle SW 12 showing possible two-voice whistle production by a common bottlenose dolphin.
SW 12 was recorded in 3 different years during 7 encounters/days (2011: A–D, 2012: E–F, 2013: G). Frequency (kHz) is on the y-axis and ranges from 0 to 24 kHz. Time (s) is on the x-axis. The scaling is the same for all spectrograms. Spectrogram settings: FFT 512, Hanning window, overlap 50%. Note reverberation of whistle in spectrogram A. Loops are highlighted by boxes in spectrogram G: HF = High frequency contour, DS = Down-sweep contour.
Table 3.
Mean ±SD (CV) acoustic parameters of signature whistle types (n = 20) from Walvis Bay bottlenose dolphins.
Figure 3.
GAM response curve showing the effect of group size on the diversity of signature whistle types of common bottlenose dolphins from Namibia.
Generalized additive model response curve showing smoothed fit of the relationship between signature whistle type diversity and group size per encounter, controlled for calf presence. The plot controls for the relationship of other variables, and is a result of back-fitting the algorithm used by the R-function GAM to calculate the additive contribution of each variable using nonparametric smoothing methods. Note that the y-axis is on the scale of the link function, not the measured variable. Points represent the residuals, the solid line represents the function estimated by the GAM and the area in grey shows the 95% confidence interval.
Table 4.
Summary of GAM output investigating the diversity of signature whistle types of common bottlenose dolphins from Namibia.