The Evolution of Auditory Adaptations for Aquatic Life in Pinnipeds

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Pinnipeds (seals, sea lions, and walruses) are key top predators of marine ecosystems that share a remarkable adaptation: the ability to hear in-air and underwater. This amphibious hearing ability, unique in mammals, is a result of their evolutionary transition from land to life underwater. Pinniped amphibious hearing is possible thanks to an organ in their ear called the cavernous sinus, which led to a diverse array of adaptations in the bony ear of pinnipeds during their evolution. The bioacoustics of pinnipeds has been the subject of many recent studies. However, none of this research has been linked to their auditory anatomy, which has barely been explored. In this project I will explore the evolution of the highly specialised auditory anatomy of pinnipeds by: (1) digitising and visualising the bony ear regions of pinnipeds (both living and extinct) and their close relatives (ursids and mustelids) via high-resolution micro-CT scanning; (2) reviewing the diversity of auditory adaptations in pinnipeds linked to underwater hearing; (3) quantitatively analysing pinniped inner ears via 3D geometric morphometrics; (4) identifying convergent evolution among pinnipeds towards the ability to hear ultrasonic sounds; (5) investigating the origin of amphibious hearing in pinnipeds using phylogenetic comparative methods. This project will result in the most comprehensive 3D digital dataset of the bony ear anatomy of pinnipeds. This project will establish a foundational link between morphological and bioacoustic studies in pinnipeds, providing profound insights into how their unique amphibious hearing evolved. During this project I will gain expertise in 3D geometric morphometrics and phylogenetic comparative methods, and experience in open science practices, mentorship, teaching, natural history collection management, and other transferable skills that will substantially improve my future career prospects, firmly establishing me as an independent researcher.