The Evolution of Auditory Adaptations for Aquatic Life in Pinnipeds
Lead Research Organisation:
Natural History Museum
Department Name: Life Sciences
Abstract
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.
Publications
Kotevski J
(2024)
A megaraptorid (Dinosauria: Theropoda) frontal from the upper Strzelecki Group (Lower Cretaceous) of Victoria, Australia
in Cretaceous Research
Rule JP
(2023)
Giant baleen whales emerged from a cold southern cradle.
in Proceedings. Biological sciences
| Description | 1. What were the most significant achievements from the award? So far, the UKRI SEAL project has gathered the most comprehensive dataset of seal auditory morphology to date, consisting of photos, linear measurements, and micro-CT scans. The Micro-CT scan data alone represents roughly 4.5 terabytes of data. Preliminary findings include using dissection data to confirm the presence of the cavernous sinus (the organ that enables amphibious hearing in seals) in both true seals and fur seals/sea lions. Several bony correlates for the presence of the sinus have been found, which can be used to confirm the presence or absence of the sinus in fossil seals. Preliminary analysis of 3D inner ear data generated from scans shows a clear difference in inner ear morphology between terrestrial and aquatic species, with the true seals possessing specialised morphology for high frequency hearing. Data on the middle ear region that was processed as part of a Masters project shows a clear adaptation for underwater hearing in seals as a result of the presence of the cavernous sinus. Results are currently being written up as several publications, which will serve as avenues to communicate all findings directly addressing the objectives of the project. The collaborative network for the project has expanded to include colleagues from France, Germany, United States of America, Australia, and New Zealand. 2. To what extent were the award objectives met? If you can, briefly explain why any key objectives were not met. The project is still ongoing, and analyses are being finalised. However, based on preliminary data, we expect objectives 1, 2, & 3 to be addressed. Some final bioacoustic data is being gathered from previously accumulated databases to test for relationships between ear morphology and vocalisations of seals; however, based on known relationships of inner ear morphology and hearing frequencies we expect to find some correlations. The 3D dataset is being close to finalised, with most in-house scanning finished despite some internal delays due to scheduling issues. The final part of the dataset is being provided by external collaborators in France, Germany, and the USA. Delays in these final portion of the dataset will not affect the objectives being delivered, as the current dataset is sufficient to run analyses suitable for publication. During the duration of the fellowship, a publication investigating similar questions to our UKRI SEAL project was published (https://doi.org/10.1093/zoolinnean/zlad014). Whilst the paper partially addresses some questions in Objective 3 of our fellowship, it does not include information on amphibious hearing or fossil data. We have invited several authors of this paper to contribute their data to the project, in order to help deliver our objectives. |
| Exploitation Route | We expect the future research findings to be taken up by the marine bioacoustic research community, as it will highlight the bioacoustic diversity in seals. We expect that this will lead to renewed interest in collecting baseline bioacoustic data from multiple seal species which remain unstudied (e.g. the Mediterranean monk seal). Expanding on from this, we envisage that this may ultimately lead to more informed policy decisions regarding the regulation of underwater noise pollution in environments occupied by seals. |
| Sectors | Environment Culture Heritage Museums and Collections |
| Description | NHM (Natural History Museum) Generation Hope |
| Form Of Engagement Activity | Participation in an open day or visit at my research institution |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Schools |
| Results and Impact | Outreach event NHM Generation Hope on seal biology and conservation, intended to communicate messages related to the planetary emergency. During this event, I discussed seal biology, including underwater hearing, with members of the public and school groups using museum specimens. Roughly 200-300 individuals engaged with the table. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.nhm.ac.uk/events/generation-hope.html |
| Description | NHM Nature Live presentation "Seal Superpowers" |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Public/other audiences |
| Results and Impact | NHM Nature Live presentation "Seal Superpowers" on the adaptations of seals. During this public presentation (roughly 100 people in attendance), I participated in a Q&A style discussion about the adaptations of seals to life underwater, including their amphibious hearing abilities. Afterwards members of the public engaged in a Q and A on seal hearing. |
| Year(s) Of Engagement Activity | 2023 |