Hearing Loss in Stranded Odontocete Dolphins and Whales

Abstract

The causes of dolphin and whale stranding can often be difficult to determine. Because toothed whales rely on echolocation for orientation and feeding, hearing deficits could lead to stranding. We report on the results of auditory evoked potential measurements from eight species of odontocete cetaceans that were found stranded or severely entangled in fishing gear during the period 2004 through 2009. Approximately 57% of the bottlenose dolphins and 36% of the rough-toothed dolphins had significant hearing deficits with a reduction in sensitivity equivalent to severe (70–90 dB) or profound (>90 dB) hearing loss in humans. The only stranded short-finned pilot whale examined had profound hearing loss. No impairments were detected in seven Risso's dolphins from three different stranding events, two pygmy killer whales, one Atlantic spotted dolphin, one spinner dolphin, or a juvenile Gervais' beaked whale. Hearing impairment could play a significant role in some cetacean stranding events, and the hearing of all cetaceans in rehabilitation should be tested.

Staat van de natuur van Caribisch Nederland 2017 : een eerste beoordeling van de staat (van instandhouding), bedreigingen en managementimplicaties van habitats en soorten in Caribisch Nederland

“…Alhoewel visserij minder problematisch is binnen de wateren van Caribisch Nederland (maar meer direct daarbuiten, zoals Venezolaanse wateren), neemt menselijke verstoring wel gestaag toe (Debrot et al, 2011b), met aantoonbaar negatieve effecten, zoals aanvaringen en gehoorschade met strandingen tot gevolg (Mann et al, 2010;Luksenburg, 2014). Daarvoor dienen wettelijke richtlijnen te worden opgesteld en dient verder onderzoek te worden gedaan naar de mate van antropogene geluidsbelasting in zee (Risch en de Haan, 2016).…”

Possible age-related hearing loss (presbycusis) and corresponding change in echolocation parameters in a stranded Indo-Pacific humpback dolphin

“…Hearing loss has previously been documented in odontocete species in both captive (Ridgway and Carder, 1997;Brill et al, 2001;Finneran et al, 2005b;Yuen et al, 2005;Houser and Finneran, 2006;Houser et al, 2008) and stranded conditions (Mann et al, 2010). Assuming that the auditory system of odontocetes is similarly subject to impairment/hearing loss as reported in humans and other mammals, hearing loss in odontocetes can be caused by intense chronic noise, transient intense noise exposure, congenital hearing impairment, physical trauma, infections of the inner ear, ototoxic drug treatment and presbycusis (Tarter and Robins, 1990).…”

“…It follows that hearing loss in odontocetes is an increasingly important consideration. While there is some information on the fundamental hearing ability of many odontocete species (Au et al, 2000;Mooney et al, 2012), hearing loss has only been investigated and demonstrated in a few species in captivity (Ridgway and Carder, 1997;Brill et al, 2001;Finneran et al, 2005b;Yuen et al, 2005;Houser and Finneran, 2006;Houser et al, 2008) or while stranded (Mann et al, 2010). Little is known about the incidence and cause of the reported hearing loss in odontocetes, and differences across species and habitat conditions.…”

Priorities in management implementation for marine mammal conservation in the Saba sector of the Yarari sanctuary

“…pulses. Van Bree and Kristensen (1974) were the first to suggest that naval exercise-related marine noise might be a cause of mortality of cetaceans in the Dutch Caribbean while Mann et al (2010) appear to have determined an instance of hearing loss as a potential cause of stranding of a pilot whale in Curaçao.…”