Cornwall Mammal Group
Coastal Otter Project
Otter Spraint
Between 2018 and 2020 Dave Groves and Rebecca Smith co-ordinated the Cornwall Coastal Otter Project. Following up an increasing number of reports of otters seen in estuaries and around our coastline we wanted to find out if these animals were just moving between river catchments or if they were actively feeding in the sea, in the same way that otters use marine habitats around the Scottish coast.
Otters use their droppings to mark territories and we know that food passes rapidly through the digestive tract of the otter leaving evidence of their diet in the form of bones and other fragments. Thirty volunteers collected 223 spraint samples from 111 sites around Cornwall, some on the coast, others on estuaries and others inland. Spraints were cleaned and sorted and the contents analysed to determine what the otters had been eating.
We found marine fish remains in 62% of samples but also evidence of freshwater or terrestrial prey in 79% of samples showing that otters were feeding in both environments. Further from the coast the proportion of marine prey fell sharply – indicating otters at the coast are not just visiting but remaining at the coast for extended periods. We have presented our findings at several conferences and the work has been published in the journals of the Mammal Society. You can read more in the below publications:
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Cornwall Mammal Group Poster, Return to the Shore: The diet of Eurasian Otter (Lutra lutra) around the coastal fringe of Cornwall.
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Groves, D. & Smith., R.J. (2021) The diet of Eurasian otters (Lutra lutra) around the coastal fringe of Cornwall. Mammal Communications 7: 11-16. DOI: 10.59922/CKRT8363
As part of the project we have also produced a reference manual to help identify common prey species in spraint – this manual is available HERE.
Rebecca Smith sadly passed away in January 2020 – we have dedicated this project to Rebecca, recognising her incredible contribution and hopefully inspiring other students.