Newborn harbour porpoises attain full hearing abilities the fastest

Mother calf and her baby (c) S. Koschinski

Fastest hearing development among mammals Although all mammals have the ability to hear, it is not something that is fully developed at birth. Some species take weeks or months to fully develop this ability. A recent study has revealed that newborn harbour porpoises (Phocoena phocoena) have the fastest hearing development among mammals. A team of researchers from University of Southern Denmark discovered that harbour porpoises take less than 30 hours to fully develop their hearing abilities – this is the fastest in any studied animal. According to biologist Magnus Wahlberg, hearing is the most important of the senses for a porpoise, both for adults and calves, so it is logical that a newborn calf spends energy on fine tuning and optimising its hearing as fast as possible. He and his colleagues Lara Delgado-García (also from SDU) and Jakob Højer Kristensen from the research and experience center Fjord&Bælt in Kerteminde, Denmark have published a study on their discovery in Journal of Comparative Physiology A. The study involved two newborns (age 1-4 days old) and three adults from the Fjord&Bælt center. The biologists non-invasively measured their auditory brainstem response, stimuli consisting of clicks centered at 130 kHz, which is the species' frequency band used for echolocation and communication. At the end of the study, the scientists were not able to detect any significant differences in the hearing of the newborn and adult porpoises. With the new knowledge about porpoise hearing development, the researchers expect other toothed whales to have the same ability. This new information is important in understanding the sensory development of newborn toothed whales shaped by evolution, as well as for designing efficient protection mechanisms and legislations for species prone to disturbance by anthropogenic noise from windmills, shipping traffic, etc.

Harbour porpoises (c) Sophia Wenger