Clicks of a Newborn Bottlenose Dolphin (Tursiops truncates)

Abstract

Toothed whales and dolphins produce complex acoustic signals. However, how they develop and function is unclear. In this study, the sounds of a newborn (NB) bottlenose dolphin (Tursiops truncatus) were recorded by a dual-channel recording system in the 0.4–220 kHz frequency band with a dynamic range of 81 dB and sampling frequency of 1 MHz, simultaneously with video recording of its position with respect to hydrophones, 22, 46, 46.5 and 47 h after birth. The results of the analysis of the recordings indicate that the NB produced 20 series containing 1640 echolocation clicks. In doing so, it varied the duration of series in the range of 0.8–7 s, the number of clicks in a series from 20 to 280 and the interpulse intervals from 6 to 220 ms. When moving along the pool, it shifted the position of the maximum of the click radiation direction in space, and each subsequent click was produced after receiving an echo from the previous one and a time delay (tens of ms) for echo processing. The spectral and temporal characteristics of its clicks differ slightly from those of adult dolphins. The apparent source level of clicks (ASL) at a distance of 1 m from the NB was 188–164 dB re 1 μPa. Consequently, the abilities of the NB bottlenose dolphin (Tursiops truncatus) to echolocate, considered for the first time for toothed whales in this paper, are innate, while physiological, social, and cognitive aspects of echolocation, which are not considered in this paper, apparently still require development.