Student Spotlight – Sarah du Plessis
PhD Research at Cardiff University
*Content warning: graphic images of otter roadkill and examinations featured below*
I never quite know how the conservation is going to go when people ask me ‘What’s your PhD on?’. Sometimes we get straight into the nitty gritty of the population history of otters in the UK, ‘Where did they come from in Europe?’, ‘Are Scottish otters different to Cornish otters?’. Sometimes we discuss how cute they are, and where you can see them, and sometimes I’m asked straight away ‘How do you get your samples?’. The surprising truth is, mostly from roadkill.
It’s not always pleasant, and it’s generally not what people expect, but in reality, road traffic accidents (RTAs) with wildlife are a significant cost of road network expansions. Although a loss for the wild population, it is possible to use these otters in research, which would not otherwise be possible for the species.
The Eurasian otter (Lutra lutra) population collapsed in the UK (and across much of Europe) from the 1950s to 1980s due to the accumulation through the food chain of harmful pesticides (bioaccumulation) in the apex predator of our waterways. Following the ban of some of these chemicals, the population started to recover, expanding across the UK through the 90s to the point where, currently, otters are found across much of the UK. Although this is excellent news for UK otters, it has illustrated the elevated risk of environmental pollution to our apex predators, such as the otter. Equally, and importantly, this provides an opportunity to monitor environmental pollution at early stages, when contaminants are at barely detectable levels in the environment, but detectable in the otters where they bioaccumulate.
During the collapse, otter populations in the UK became small and spatially isolated from one another, creating four ‘stronghold’ populations that persisted. These were in the south west of England, west of Wales, east of England, and north of the UK (including north of England and Scotland). Genetic analyses of the populations after they had recovered show signals of this population structuring, suggesting strong genetic differences between otters from these strongholds (Stanton et al. 2014). However, it is unclear what the UK population looked like before the population collapse and whether the genetic differences between these areas have arisen since the population crash (for example due to ‘bottleneck’ effects) or whether there were pre-existing differences (for example due to local adaptations to different environments).
As a part of the 25 Genomes Project and Darwin Tree of Life Project, the Wellcome Sanger Institute has produced a platinum quality reference genome of a male otter from Somerset, sampled by the Otter Project (Mead et al. 2020). This reference genome makes any future genomics research into the species simpler, more accessible and of a higher accuracy, as any additional genomics samples are compared to this reference genome. My PhD is building on previous genetic analyses, using the new reference genome and whole genome sequencing of samples across the UK and Eurasia to assess the population history of otters in the UK and across their Eurasian range.
To collect tissue samples from live otters would require trapping, which is an inherently risky and stressful process for the animal and would be ethically questionable as well as logistically extremely challenging. Instead, the Cardiff University Otter Project work with organisations including the Environment Agency (EA), Natural Resources Wales (NRW) and the International Otter Survival Fund (IOSF), to collect roadkill otters and send them to Cardiff for post-mortem examination. This network relies on members of the public reporting otters found dead from across Great Britain to facilitate the research the Otter Project conducts. During post mortems we collect a variety of measurements and descriptions of the otter, and a range of samples for research, such as liver for contaminant analysis and muscle samples for genetics. The Otter Project has been running since 1994, and we are approaching our 4000th otter, however we are still lacking otters from some areas. On the map of Great Britain below, each blue tag is an otter in the Otter Project database, and although we have some regions such as Wales and Somerset well sampled, other regions such as the south east of England and parts of Scotland are only sparsely represented.
So, I end this post with a plea for help! Wherever you are based in the UK, if you ever see a dead otter, please report it to your local organisation, or email the otter project at firstname.lastname@example.org. In England, please contact the EA, in Wales its NRW and in Scotland the IOSF (see QR codes and phone numbers above). If you would like to get involved in research with the Otter Project, for example as a Masters or PhD student, or make use of our archive of samples and data, or if you’d like to apply to be one of our team of undergraduate placement students who maintain the project every year, just drop us an email. To hear more about what we get up to check out our website, follow us on facebook and twitter, and sign up for our newsletters.
Many thanks to my supervisors (Drs Frank Hailer, Liz Chadwick and Klaus-Peter Koepfli), my funders (NERC GW4+), our sequencing collaborators (Wellcome Sanger Institute) and all the members of public, volunteers and students involved in running the Otter Project since 1994.
Mead, D., Hailer, F., Chadwick, E., Miguez, R. P., Smith, M., Corton, C., Oliver, K., Skelton, J., Betteridge, E., Doulcan, J., Dudchenko, O., Omer, A., Weisz, D., Aiden, E. L., Mccarthy, S., Howe, K., Sims, Y., Torrance, J., Tracey, A. and Challis, R. 2020. The genome sequence of the Eurasian river otter, Lutra lutra Linnaeus 1758. Wellcome Open Research 5. https://doi.org/10.12688/wellcomeopenres.15722.1
Stanton, D. W. G., Hobbs, G. I., McCanfferty, D. J., Chadwick, E. A., Philbey, A. W., Saccheri, I. J., Slater, F. M. and Bruford, M. W. 2014. Contrasting genetic structure of the Eurasian otter (Lutra lutra) across a latitudinal divide. Journal of Mammalogy 95(4), pp. 814-823. https://doi.org/10.1644/13-MAMM-A-201