Seals are known for their impressive adaptation to marine life, but a new international investigation reveals that one of their greatest trump cards may lie in their ears. A study published in the scientific journal Proceedings of the Royal Society B: Biological Sciences concluded that these mammals developed the ability to hear effectively in both aquatic and terrestrial environments about 26 million years ago.
The investigation, led by scientists from Monash University, in Australia, identified the role of a specialized tissue present in the ears of seals, which allows them to process sounds in two radically different acoustic environments. The results suggest that this capability, known as amphibious hearing, is a fundamental feature of the evolution of pinnipeds — the group that includes seals, sea lions, and walruses.
“Seals have a superpower: they can hear and communicate both on land and in the ocean,” says James Rule, the study’s principal author. “Most mammals cannot hear properly underwater, but seals have developed specialized ears to do so without losing their hearing ability on land.”
To reach these conclusions, the researchers analyzed three-dimensional models of ears obtained through computed tomography, combining data from living species with fossils preserved in museum collections. Among the specimens studied is Pithanotaria starri, an early sea lion species that lived about 10 million years ago and that already exhibited characteristics associated with amphibious hearing.
According to the authors, the evolutionary challenge was particularly complex because sound behaves very differently in water and air. Generally, auditory structures adapted to one environment tend to function poorly in the other. Seals, however, managed to overcome this limitation through a dual-function auditory system.
“They developed a highly specialized system capable of functioning efficiently in both environments,” explains Natalie Cooper, researcher at the Natural History Museum in London and co-author of the study. “They can process high-frequency sounds underwater and maintain sharp directional hearing both in the ocean and on land.”
The researchers argue that this adaptation helped drive the vocal diversity observed in present-day pinnipeds, enabling them to communicate in different ecological contexts, from coastal colonies to deep marine environments.
For Alistair Evans, director of the EvoMorph research group at Monash University, this capacity represents a unique evolutionary advantage. “Seals are the only animals in their group to have developed this sensory flexibility. They can switch between two completely distinct acoustic worlds without loss of performance, whether resting, hunting, or communicating.”
The authors consider that the discovery helps to better understand the evolution of marine mammals and the way some species have managed to adapt successfully to extremely different environments, preserving abilities essential to their survival.
