title: Possible age-related hearing loss (presbycusis) and corresponding change in echolocation parameters in a stranded Indo-Pacific humpback dolphin.
abstract: The hearing and echolocation clicks of a stranded Indo-Pacific humpback dolphin (Sousa chinensis) in Zhuhai, China, were studied. This animal had been repeatedly observed in the wild before it was stranded and its age was estimated to be ~40 years. The animal's hearing was measured using a non-invasive auditory evoked potential (AEP) method. Echolocation clicks produced by the dolphin were recorded when the animal was freely swimming in a 7.5 m (width)×22 m (length)×4.8 m (structural depth) pool with a water depth of ~2.5 m. The hearing and echolocation clicks of the studied dolphin were compared with those of a conspecific younger individual, ~13 years of age. The results suggested that the cut-off frequency of the high-frequency hearing of the studied dolphin was ~30-40 kHz lower than that of the younger individual. The peak and centre frequencies of the clicks produced by the older dolphin were ~16 kHz lower than those of the clicks produced by the younger animal. Considering that the older dolphin was ~40 years old, its lower high-frequency hearing range with lower click peak and centre frequencies could probably be explained by age-related hearing loss (presbycusis).
authors.affiliation: Tropical Marine Science Institute, National University of Singapore, 18 Kent Ridge Road, Singapore 119227.
authors.forename: Songhai
authors.initials: S
authors.lastname: Li
authors.forename: Ding
authors.initials: D
authors.lastname: Wang
authors.forename: Kexiong
authors.initials: K
authors.lastname: Wang
authors.forename: Matthias
authors.initials: M
authors.lastname: Hoffmann-Kuhnt
authors.forename: Nimal
authors.initials: N
authors.lastname: Fernando
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Taylor
authors.forename: Wenzhi
authors.initials: W
authors.lastname: Lin
authors.forename: Jialin
authors.initials: J
authors.lastname: Chen
authors.forename: Timothy
authors.initials: T
authors.lastname: Ng
mesh_terms: D000818:Animals; D002681:China; D004289:Dolphins; D004455:Echolocation / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000502:physiology; D006320:Hearing Tests / Q000662:veterinary; D008297:Male; D011304:Presbycusis / Q000473:pathology* / Q000662:veterinary*; D013018:Sound Spectrography
keywords: auditory evoked potential; biosonar; high-frequency hearing; marine mammals