Inducing rostrum interfacial waves by fluid-solid coupling in a Chinese river dolphin (Lipotesvexillifer)

Area of Science:

• Marine biology
• Bioacoustics
• Biophysics

Background:

• The Chinese river dolphin (baiji) uses biosonar for navigation and foraging.
• Understanding sound propagation in the dolphin's head structures is crucial for biosonar function.

Purpose of the Study:

• To investigate the propagation of biosonar signals in the Chinese river dolphin (baiji).
• To analyze the role of the rostrum and associated tissues in acoustic beam formation.

Main Methods:

• Numerical solution of wave equations to model biosonar signal propagation.
• Examination of interfacial waves (compressional and shear) in the rostrum-tissue interfaces.
• Comparison of acoustic beam formation across seven different anatomical models.

Main Results:

• The baiji's rostrum acts as both an interfacial wave generator and a sound reflector.
• Rostrum-tissue interfacial waves and reflection are essential for biosonar emission.
• Models including the rostrum better replicated the complete biosonar system's beam characteristics.

Conclusions:

• The rostrum plays a critical, obbligato role in the baiji's biosonar emission.
• Interfacial waves and reflection mechanisms within the rostrum are key to acoustic beam formation.
• Findings enhance understanding of odontocete biosonar mechanisms.