Possible limitations of dolphin echolocation: a simulation study based on a cross-modal matching experiment

Chong Wei,Abel Zhong Hao Ho,Whitlow W L Au,Matthias Hoffmann-Kuhnt,Darlene R Ketten,Yu Zhang,Wen Feng,Eszter Matrai

doi:10.1038/s41598-021-85063-2

Abstract

Dolphins use their biosonar to discriminate objects with different features through the returning echoes. Cross-modal matching experiments were conducted with a resident bottlenose dolphin (Tursiops aduncus). Four types of objects composed of different materials (water-filled PVC pipes, air-filled PVC pipes, foam ball arrays, and PVC pipes wrapped in closed-cell foam) were used in the experiments, respectively. The size and position of the objects remained the same in each case. The data collected in the experiment showed that the dolphin’s matching accuracy was significantly different across the cases. To gain insight into the underlying mechanism in the experiments, we used finite element methods to construct two-dimensional target detection models of an echolocating dolphin in the vertical plane, based on computed tomography scan data. The acoustic processes of the click’s interaction with the objects and the surrounding media in the four cases were simulated and compared. The simulation results provide some possible explanations for why the dolphin performed differently when discriminating the objects that only differed in material composition in the previous matching experiments.

Highlights

Dolphins use their biosonar to discriminate objects with different features through the returning echoes
To further investigate how the shape information might be accessible to both the dolphins’ visual and echolocation senses, it is important for us to gain an understanding of what is the nature of the echoes the dolphins receive from the interrogated objects, how do they utilize the features from these echoes that provide them information about the shape, as well as whether different material compositions would interfere with their cross-modal matching ability
When the soft closed-cell foam-wrapped polyvinyl chloride (PVC) pipes were used as targets, the dolphin’s performance was again significantly better than chance (p < 0.01) and the matching accuracy rose (88.5% from 4 objects) as compared to the foam ball arrays (FB) and water-filled PVC pipes (WF) cases

Summary

Introduction

Dolphins use their biosonar to discriminate objects with different features through the returning echoes. To further investigate how the shape information might be accessible to both the dolphins’ visual and echolocation senses, it is important for us to gain an understanding of what is the nature of the echoes the dolphins receive from the interrogated objects, how do they utilize the features from these echoes that provide them information about the shape, as well as whether different material compositions would interfere with their cross-modal matching ability. Due to the slightly varied position in each trial, it was extremely difficult to determine the detailed acoustic scatter field received by the dolphin experimentally to gain insight into the experiments, a finite element analysis (FEA) was performed to provide the visualization of the underlying physical mechanisms involved in the processes of click emission and reception for cross-modal target discrimination

Objectives

Methods

Results

Discussion

Conclusion