Case study: Evidence of long-term stability in a stereotyped whistle in a single free-ranging humpback dolphin (Sousa plumbea) found in sympatry (Tursiops aduncus).

This 11-year case study describes the acoustic behaviour of a resident Indian Ocean humpback dolphin during commercial swim-with-dolphin activities in Mozambique. Combining data collected using low-cost action cameras with full bandwidth hydrophone recordings, we identified a temporally stable stereotyped whistle contour that met the SIGnature IDentification bout criteria. This whistle was produced with potential information-enhancing features (bi-phonation and subtle variations in frequency modulation). This case study provides evidence for a single, stable, stereotyped call type from a single individual in a mixed species group, contributing to the growing body of evidence for possible signature whistle use in the Sousa genus.