The distinctive forehead cleft of the Risso's Dolphin (Grampus griseus) hardly affects biosonar beam formation

Chong Wei*, Lachlan G. Gill, Christine Erbe, Adam B. Smith, Wei-Cheng Yang

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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The Risso’s dolphin (Grampus griseus) has a distinctive vertical crease (or cleft) along the anterior surface of the forehead. Previous studies have speculated that the cleft may contribute to biosonar beam formation. To explore this, we constructed 2D finite element models based on computer tomography data of the head of a naturally deceased Risso’s dolphin. The simulated acoustic near-field signals, far-field signals, and transmission beam patterns were compared to corresponding measurements from a live, echolocating Risso’s dolphin. To investigate the effect of the cleft, we filled the cleft with neighboring soft tissues in our model, creating a hypothetical “cleftless” forehead, as found in other odontocetes. We compared the acoustic pressure field and the beam pattern between the clefted and cleftless cases. Our results suggest that the cleft plays an insignificant role in forehead biosonar sound propagation and far-field beam formation. Furthermore, the cleft was not responsible for the bimodal click spectrum recorded and reported from this species.
Original languageEnglish
Article number3472
Issue number24
Publication statusPublished - 8. Dec 2022


  • Risso's dolphin
  • finite element model
  • biosonar beam formation
  • CT scan
  • echolocation
  • forehead cleft
  • Risso’s dolphin


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