This article ‘Changes in the diet of a recovering Eurasian otter population between the 1970s and 2010’ was written by David Almeida, Gordon H. Copp, Laurence Masson, Rafael Miranda, Mizuki Murai and Carl Sayer of the Department Salmon & Freshwater Team, Cefas-Lowestoft. It is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.
Changes in the diet of a recovering Eurasian otter population between the 1970s and 2010
Article first published online: 17 JAN 2012
© 2012 Crown copyright
Aquatic Conservation: Marine and Freshwater Ecosystems
Volume 22, Issue 1, pages 26–35, January 2012
How to Cite
Almeida, D., Copp, G. H., Masson, L., Miranda, R., Murai, M. and Sayer, C. D. (2012), Changes in the diet of a recovering Eurasian otter population between the 1970s and 2010. Aquatic Conserv: Mar. Freshw. Ecosyst., 22: 26–35. doi: 10.1002/aqc.1241
- Issue published online: 10 FEB 2012
- Article first published online: 17 JAN 2012
- Manuscript Accepted: 16 OCT 2011
- Manuscript Revised: 15 SEP 2011
- Manuscript Received: 3 MAR 2011
- Lutra lutra;
- spraint analysis;
- feeding tactics;
- freshwater conservation;
- angler conflict;
- species recovery
- Diet is an essential element for understanding how the Eurasian otter (Lutra lutra) is re-colonizing its former range in England following a population decline observed in the 1950s to 1970s.
- Otter spraints from the River Glaven catchment (north Norfolk, eastern England) were collected seasonally between 2009 and 2010 from three habitat types (ponds, ‘retenus’ (small in-stream reservoirs), and stream stretches). Feeding tactics of the otter were compared between habitat types and, using previously published data, with regard to seasonal changes since the 1970s when the species was in decline.
- Otter diet composition varied greatly, with predation on aquatic invertebrates, crayfish, fish, and tetrapods. Fruit seeds were also found in the spraints. Diet generally reflected habitat, with northern pike (Esox lucius) remains found in spraints from ponds and retenus, whereas European eel (Anguilla anguilla) and gudgeon (Gobio gobio) were prominent in spraints from stream sections. Trophic diversity was particularly high in spraints collected next to ponds. Between the 1970s and the present, crayfish, brown trout (Salmo trutta), cyprinids, Eurasian perch (Perca fluviatilis), birds and mammals increased in prominence, whereas eel and threespine stickleback (Gasterosteus aculeatus) decreased, with notable seasonal variations between the study periods.
- Otter spraints revealed few prey preferences, with only that for gudgeon being ecologically relevant. The consumption of popular sport fishes, in particular common carp (Cyprinus carpio), has given rise to conflicts between recreational anglers and otter conservationists, but no demonstrated preference for carp was observed in the present study.
- Overall, otters have increased their consumption of ‘less preferred’ (i.e. lower energetic value) food types, and because the species normally preys on the most abundant species available, this suggests declines in ‘preferred’ prey types. These dietary shifts could contribute to otter dispersal and re-colonization of parts of its original European range where food availability may be higher.
© 2012 Crown copyright.