Do baby dolphins hear their parents?

La Plata Dolphin

La Plata Dolphin

Yes, according to a recent study by Lancaster and colleagues.  Many marine mammals are precocial in that the young are relatively mature and mobile from the moment of birth. Juvenile dolphins for example are independently swim, surface to breathe, and maintain contact with mother on their own.  But how developed is the hearing of a juvenile dolphin?  Are their tiny, little ears fully formed?  Alright so maybe they do not have ears per se just ear openings but you get the drift.

Dog Skull

Dolphin Skull. The auditory bullae is green.

Dog Skull

Dog Skull. Tympanic or auditory bullae in green.

Inside a vertebrate skulls, including the dolphin, is an area referred to as the tympanic or auditory bullae.  These hollow, spherical, bony structures are on the bottom, back portion of the skull and enclose parts of the middle and inner ear.  Lancaster and colleagues found in two species of dolphins, the Common Bottlenose and the La Plata, the tympanic bulla is same size in adults and juveniles, despite the smaller skulls and bodies of the young.  Why would juveniles have adult-sized “ears”?

Means and standard deviations of (a) condylobasal length, (b) tympanic bulla length, and (c) tympanic bulla height for all specimens of Pontoporia blainvillei

Means and standard deviations of (a) skull length, (b) tympanic bulla length, and (c) tympanic bulla height for all specimens of the Common Bottlenose Dolphin

The size, shape, and material of a structure determine its resonance frequency, i.e. the detectable auditory frequencies.  If dolphins vocalize at a certain frequency then the size of the tympanic bulla needs to match this—even in juveniles.  If young had a smaller ears the parents may just sound like Charlie Brown parents. As the authors state, “The fact that the overall structure of
this [auditory] architecture has remained relatively constant throughout the last 45 million
years of cetacean evolution indicates that it was an early and essential adaptation for
underwater sound reception and hearing.”

Dr. M (1801 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.

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