This project is offered as a CASE with ZSL
Marine mammals are threatened by anthropogenic impacts ranging from climate change to increased disease risk. However, examining, understanding, and forecasting marine mammal population trends is rather challenging because marine mammals are cryptic species that spend much of their time at sea, and the methods required to collect the data needed to model their populations are still in development. In particular, continuous, size-structured (e.g. body volume) population models such as integral projection models (IPMs) would enable us to gain a better understanding of their population trends. Populations of both species of pinniped that inhabit the UK, the grey seal (/Halichoerus grypus/) and the harbour seal (/Phoca vitulina/), have broadly been increasing over time. However, regional population trends and the impact of interactions between the two species remain unclear. Currently, our ability to digitise, process, and analyse the data collected by novel technology such as unmanned aerial vehicles (UAVs) is limiting our ability to investigate trends in the size and structure of UK seal populations further. In particular, seal population trends are uncertain in the Thames estuary, where harbour seal numbers were increasing but have recently started to plateau or decline. At the same time, grey seal numbers have been increasing in the Thames estuary, and it is likely that increasing grey seal numbers are contributing to the recent plateau in harbour seal numbers, although clarity here is lacking.
Our CASE partner, the Zoological Society of London (ZSL), has a monitoring program with >10 years of aerial image surveys of the Greater Thames Estuary describing grey and harbour seal population trends. This DPhil project will draw on these data, as well as collecting additional data with UAVs, to assess trends in these species over time and how they might be interacting. A component of this project will apply AI methods to further develop a UAV pipeline to estimate the body volume of a wide range of species, including pinnipeds. These data will be used to parameterise IPMs to assess seal population trends in the Greater Thames Estuary, thus significantly contributing to our understanding and conservation of key marine apex predator species in the UK. It is critical to identify local seal population declines and their contributing factors as early as possible, to apply appropriate management strategies to minimise the long-term impacts.
Recommended reading:
Stone, T. C., & Davis, K. J., (2023). An unmanned aerial vehicle pipeline to estimate body volume at scale for ecological monitoring. Biorxiv. https://doi.org/10.1101/2023.11.23.567408
Cox, T., Barker, J., Bramley, J., Debney, A., Thompson, D. & Cucknell, A. (2020) Population trends of harbour and grey seals in the Greater Thames Estuary. Mammal Communications 6: 42-51, London.]
If you are interested in this project please contact the Oxford supervisor Katrina.davis@biology.ox.ac.uk
The ZSL supervisors are
Hannah McCormick, Conservation Project Officer (ZSL): hannah.mccormick@Zsl.org
Alison Debney, Ecosystem Restoration Programme Lead (ZSL): Alison.debney@zsl.org
