Otters as sentinels for environmental health

On Wednesday 23 November 2016, Dr Elizabeth Chadwick talked to the Society about the work of the Cardiff University Otter Project, which she has managed for twelve years. The talk emphasised the otter’s importance as an indicator species for the general health of river ecosystems, and as a charismatic umbrella species that provides a focus for education and freshwater habitat conservation.

The Eurasian otter (Lutra lutra), one of 13 otter species worldwide, has an extensive range extending across continental Europe, Russia, China, and parts of north Africa; though in modern times its populations have become fragmented. In the UK, populations dramatically declined between the 1950 and 1970s, with chemicals in the environment (e.g. PCBs and organochlorine pesticides) mainly to blame. However, this protected species has recovered in the UK, and its once-isolated UK populations are again interacting. Nevertheless, by nature it is non-sociable and lives at low densities, so it can be hard to spot in the countryside.

Dr Chadwick explained the different methods used to monitor otters. The main methods used by the Cardiff University Otter Project are the monitoring of spraint (faeces and scent gland secretions) and the post-mortem of dead otters (mainly roadkill reported by the public).

A study of the spraint otters deposit at prominent locations around their territories is revealing interesting information. The spraint contains 432 volatile chemicals, and its smell is unique to an individual. The components of the spraint marking also change with age, enabling adults and juveniles to be identified.

The Cardiff University Otter Project started collecting samples from dead otters in the 1990s, when it would process around 10 otters/year (this figure is now around 200/year due to the otter’s recovery). This large sample bank now amounts to 3,000 specimens that can be used retrospectively for a wide range of interdisciplinary studies. Dr Chadwick described some of the studies that Cardiff University and its collaborators have done with these samples. These include studies on the presence of chemical contaminants over time and the effectiveness of legislation (e.g. bans on pesticides and lead), parasites infecting otters, dietary studies from stomach contents (83% fish), and genetic studies over time as a more contiguous UK population re-established. New areas of study include looking for the presence of micro-plastics and a new wave of emerging pollutants (e.g. pharmaceuticals).

For further information, visit the project’s website: www.otterproject.cf.ac.uk

Report by Stephen Nottingham