Hearing in Whales and Dolphins: Relevance and Limitations

Abstract

Understanding the hearing of marine mammals has been a priority to quantify and mitigate the impact of anthropogenic sound on these apex predators. Yet our knowledge of cetacean hearing is still limited to a few dozen species, therefore compromising any attempt to design adaptive management strategies. The use of auditory evoked potentials allows scientists to rapidly and noninvasively obtain the hearing data of species rarely available in captivity. Unfortunately, many practical and ethical reasons still limit the availability of large whales, thus restricting the possibility to effectively ensure that anthropogenic sounds have minimum effects on these species. The example of a recent Blainville's beaked whale (Mesoplodon densirostris) audiogram collected after a stranding indicated, for instance, very specialized hearing between 40 and 50 kHz, which corresponded to the frequency-modulated upsweep signals used by this species during echolocation. The methods used during a stranding event are presented along with the major difficulties that have slowed down the scientific community in measuring the audition of large whales and the potential value in obtaining such results when successful.

Humpback whales Megaptera novaeangliae alter calling behavior in response to natural sounds and vessel noise

“…Anthropogenic sounds are recognized as a threat to acoustically oriented species across taxa in both the marine and terrestrial realm (Patricelli & Blickley 2006, Popper & Hastings 2009, Kight & Swaddle 2011, Potvin et al 2011, Finneran 2015, Pacini & Nachtigall 2016, Simpson et al 2016. Pervasive sound has the potential to limit acoustic communication, elicit changes in foraging behavior, alter preda-tor−prey dynamics, and have negative physiological impacts (Weilgart 2007, Potvin et al 2011, Rolland et al 2012, Richardson et al 2013, Finneran 2015, Simpson et al 2016).…”

Marine bioacoustics

“…In dolphins, the reception of sound pressure depends on the lower jaw and associated fatty tissue. For a limited number of species within these groups, sound reception has been characterized by both auditory evoked potentials and behavioural audiograms showing hearing sensitivity and range strongly related to communication and echolocation vocalizations (Pacini and Nachtigall, 2016). Hearing is not just about acoustic reception: new approaches are now opening up the fascinating study of acoustic behaviour and perception.…”