The Source Parameters of Echolocation Clicks from Captive and Free-Ranging Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis).

Liang Fang,Yongtao Li,Ding Wang,Zhaolong Cheng,Kexiong Wang,Matthew K Pine,Songhai Li,Andreas Fahlman

doi:10.1371/journal.pone.0129143

Abstract

The clicks of Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis) from 7 individuals in the tank of Baiji aquarium, 2 individuals in a netted pen at Shishou Tian-e-zhou Reserve and 4 free-ranging individuals at Tianxingzhou were recorded using a broadband digital recording system with four element hydrophones. The peak-to-peak apparent source level (ASL_pp) of clicks from individuals at the Baiji aquarium was 167 dB re 1 μPa with mean center frequency of 133 kHz, -3dB bandwidth of 18 kHz and -10 dB duration of 58 μs. The ASL_pp of clicks from individuals at the Shishou Tian-e-zhou Reserve was 180 dB re 1 μPa with mean center frequency of 128 kHz, -3dB bandwidth of 20 kHz and -10 dB duration of 39 μs. The ASL_pp of clicks from individuals at Tianxingzhou was 176 dB re 1 μPa with mean center frequency of 129 kHz, -3dB bandwidth of 15 kHz and -10 dB duration of 48 μs. Differences between the source parameters of clicks among the three groups of finless porpoises suggest these animals adapt to their echolocation signals depending on their surroundings.

Highlights

The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is a member of the Phocoenidae family
A total of 66 sound files (100 s each) containing vocalizations were recorded from the Baiji aquarium experimental group, from which 68 on-axis echolocation clicks were analyzed
The average (± SD) distances between the sound source and receiving hydrophone was 4 ± 1 m, 12 ± 5 m and 29 ± 26 m within the Baiji aquarium, Shishou Tian-e-zhou Reserve and Tianxingzhou experimental groups, respectively (Table 1)

Summary

Introduction

The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is a member of the Phocoenidae family It has a body length between 140 and 133 cm, weighs between 40 and 70 kg and reaches sexual maturity at 4.5 and 4 years in males and females respectively [1,2]. This subspecies is critically endangered and is exclusively freshwater, endemic to the middle and lower reaches of the Yangtze River in China, as well as two connecting lakes (i.e., Poyang Lake and Dongting Lake) [3]. The Yangtze finless porpoise navigates the underwater environment using high frequency echolocation clicks (> 70 kHz) [4].

Methods

Results

Conclusion