Great cormorants (Phalacrocorax carbo) can detect auditory cues while diving

Naturwissenschaften. 2017 Jun;104(5-6):45. doi: 10.1007/s00114-017-1467-3. Epub 2017 May 5. Hansen KA1, Maxwell A2, Siebert U3, Larsen ON2, Wahlberg M2. Author information 1 Department of Biology, Marine Biological Research Center, University of Southern Denmark, Hindsholmvej 11, 5300, Kerteminde, Denmark. kirstinhansen@biology.sdu.dk. 2 Department of Biology, Marine Biological Research Center, University of Southern Denmark, Hindsholmvej 11, 5300, Kerteminde, Denmark. 3 Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, 30173, Hannover, Germany. Abstract In-air hearing in birds has been thoroughly investigated. Sound provides birds with auditory information for species and individual recognition from their complex vocalizations, as well as cues while foraging and for avoiding predators. Some 10% of existing species of birds obtain their food under the water surface. Whether some of these birds make use of acoustic cues while underwater is unknown. An interesting species in this respect is the great cormorant (Phalacrocorax carbo), being one of the most effective marine predators and relying on the aquatic environment for food year round. Here, its underwater hearing abilities were investigated using psychophysics, where the bird learned to detect the presence or absence of a tone while submerged. The greatest sensitivity was found at 2 kHz, with an underwater hearing threshold of 71 dB re 1 μPa rms. The great cormorant is better at hearing underwater than expected, and the hearing thresholds are comparable to seals and toothed whales in the frequency band 1-4 kHz. This opens up the possibility of cormorants and other aquatic birds having special adaptations for underwater hearing and making use of underwater acoustic cues from, e.g., conspecifics, their surroundings, as well as prey and predators. KEYWORDS: Aquatic birds; Psychophysics; Sensory adaptation; Threshold; Underwater acoustics PMID: 28477271 DOI: 10.1007/s00114-017-1467-3 [Indexed for MEDLINE]