EAPSI: Measuring the hearing and echolocation characteristics of a Risso's dolphin

Smith Adam B, Honolulu HI

Investigators

Abstract

All toothed whales and dolphins possess highly developed hearing and biosonar systems that cannot be replicated even with modern technology. These exceptional capabilities are the result of extremely specialized anatomical structures in the head. A better understanding of these systems in toothed whales may lead to improved technological advancements for signal processing, sonar techniques, medical imaging devices, and cochlear implants. One species of dolphin, the Risso's dolphin, has evolved a unique vertical crease on its forehead which is absent in other dolphin species. Although the function of this crease is unknown, its location on the head indicates it likely plays an important role in the hearing or echolocation systems. Detailed study of these systems requires the cooperation of a trained captive subject animal. In collaboration with Dr. Jack Wei-Cheng Yang at National Chiayi University in Taiwan, this project will investigate the function of the melon crease by measuring the hearing capabilities and echolocation sounds of a trained captive Risso's dolphin at Farglory Ocean Park in Hualien, Taiwan, one of only three captive individuals of this species in the world. Proposed experiments for this project will 1) measure the hearing sensitivities of the animal to acoustic stimuli presented at different points on the animal's head, and 2) measure acoustic characteristics of the echolocation beam in the near and far sound field. Hearing measurements will be conducted using non-invasive Auditory Brainstem Response (ABR) methodology, which measures nerve impulses from the brainstem in response to the reception of sound. Echolocation beam patterns in the near and far field will be recorded using a variable array of synchronized hydrophones. The proposed study would represent the first description of the hearing pathways and echolocation beam patterns in the Risso's dolphin and the first step toward studying the functional morphology of the melon cleft. This NSF EAPSI award is funded in collaboration with the National Science Council of Taiwan.