Figure 1.
Exemplary calls for the vocal repertoire of giant otters.
Calls were obtained from wild and captive individuals. The spectrograms depict frequency over time and were generated using a 1024-point FFT and a Hann window with 75% overlap. The oscillograms show pressure changes over time. a) Cohesion: contact and coordination calls. From left to right: bark, close call, contact call, contact call gradation, hum, hum gradation, hum short, isolation call, whistle, whistle double, and underwater call. b) Alarm calls. From left to right: growl, hah!, snort, and wavering scream. c) Begging calls. From left to right: ascending scream, begging call, begging scream, begging scream gradation, and whine. d) Other calls. From left to right: mating call and suckling call.
Figure 2.
Signal space of the giant otters’ adult vocal repertoire defined by the first two discriminant functions.
Symbols indicate group centroids. Discriminant function 1 was mainly shaped by the peak frequency within subunit 1 and the fundamental frequency at 1/3 duration of the entire call (combined in one principal component). Discriminant function 2 was mainly shaped by the average entropy in the subunits 2 and 3 (combined in another principal component).
Table 1.
Description of the giant otters’ vocal repertoire and behavioural context.
Table 2.
Assessment of model fit of the discriminant function analysis.
Table 3.
Percentage of misclassified cases in the cross-validated DFA, listing the vocalizations with which the misclassified cases have been confused by the DFA*.
Figure 3.
Exemplary calls from neonate giant otters.
Vocalizations were recorded from one wild and one captive litter. The spectrograms depict frequency over time and were generated using a 1024-point FFT and a Hann window with 75% overlap. The oscillograms show pressure changes over time. a) Begging call-like vocalization. b) Contact call-like vocalizations. c) Distress call 1. d) Hums. From left to right: bark-like call, hum-like call, and distress call 2. e) Hum gradation-like vocalization. f) Suckling call. g) Whistles. From left to right: high whistle, whistle, and low whistle.
Table 4.
Structural description of the neonate giant otter vocal repertoire.