Are low frequency sounds a marine hearing hazard: a case study in the Canary Islands [abstract]

TitleAre low frequency sounds a marine hearing hazard: a case study in the Canary Islands [abstract]
Publication TypeJournal Article
Year of Publication1998
AuthorsAndre, M. C., C. Kaminga, and D. R. Ketten
JournalBioacoustics Journal
Start Page220
Date Published12/1998
Type of ArticleScientific
Keywordsambient noise, auditory pathology, Canary Islands, hearing, hearing loss, hearing pathology, marine mammals, noise, noise exposure, physeter catadon, physeter macrocephalus, physeteridae, ship strike, shipping, sperm whale

Shipping has been responsible recently for many collisions with cetaceans in the Canary Islands. A series of experiments, including the playback of artificial sounds of different frequencies, was conducted to test a system designed to keep sperm whales apart from the ferries routes. The results showed that the whales did not react to low frequency playbacks which suggests sperm whales from an area which has heavy vessel traffic have a high tolerance for noise. After the collision of a ferry with two sperm whales, ears were extracted from the two individuals, in order to assess the health of their inner ears. CT scans showed that there were no fractures or other overt evidence of impact, or ship strike related injuries; however, ears from both animals had reduced auditory nerve volumes. 0ne animal also had patches of dense tissue in the inner ear. These findings are consistent with auditory nerve degeneration and fibrous growth in response to inner ear damage. In combination with the results from the playback experiment, these results suggest that low frequency sounds from shipping may be affecting hearing and increasing collision rates. These findings are however, preliminary, and histologic analyses are underway to determine whether the primary cause of the ear changes seen with CT are disease or noise induced.