A review on bio-sonar behaviour research of Yangtze finless porpoise using animal bone acoustic data loggers

Abstract

In recent 10 years, a miniature stereo acoustic data logger (A-tag, W20-AS, Little Leonardo, Japan) has been used to observe the bio-sonar behaviour of free-ranging Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis). The A-tag is small enough to be attached on the one of the smallest odontocetes by using suction cups. The A-tag with two external hydrophones can record the sonar pulse intensity, inter-click-intervals, and sound source direction measured by time arrival difference of sounds at the two hydrophones. Major outcomes by A-tag were the in situ off-axis sonar beam pattern, attention and approach phase of biosonar behaviour, scanning sonar of rolling animals, and social contacts among free-ranging Yangtze finless porpoises. In addition, frequent ultrasonic sound production was confirmed that seemed to be a reason of high detection performance of this species using passive acoustic monitoring of finless porpoises. This biosonar monitoring method using miniature data logger system de...