Dr Elizabeth Chadwick - PhD
Cardiff University Otter Project is a national scheme collecting otters found dead in England and Wales for post mortem examination. The project was established in 1992 with the aim of using tissues collected from this top predator to monitor aquatic contamination. The opportunities presented by national collection of a European protected species are considerable, and while contaminant monitoring remains a key aspect of the project, a wide diversity of additional research is now undertaken under the umbrella of CUOP.
As a nocturnal and elusive species, the Eurasian otter is extremely difficult to study in the wild. Samples collected from animals found dead therefore form a key resource, enabling us to investigate aspects of their ecology and health that would otherwise be inaccessible. In addition to an intrinsic interest in the species from a conservation perspective, the otter has an interesting ecological role at the interface between terrestrial and aquatic habitats, and is at the top of the freshwater aquatic food chain. It is therefore a useful model organism, and can be used to investigate key ecosystem and population processes.
The project now receives >200 otters each year, from which we collect and archive a wide range of tissues and data. These form an ever-expanding collection of material that is used by national and international collaborators and PhD students.
1. Health and contamination
Most otters received are road traffic mortalities, which typically sample a healthy sector of the population. During post mortem, a range of health indicators are recorded, including body condition, abnormalities, or signs of infection / disease (e.g. tumours, kidney stones). Current parasitological research (PhD student Eleanor Sherrard Smith, Cardiff University) focuses on two species of biliary parasite thought to be recent introductions to the UK, as well as spatial and temporal variation in ectoparasites including Ixodes ticks. Parasite-bourne disease is currently the focus of two collaborative studies; one (Dan Forman, Swansea University) screening blood samples for Toxoplasmosis, and the other (Richard Birtles, Liverpool University) focusing on tick-bourne disease, such as Bartonella, Anaplasma, Ehrlichia, and Babesia.
Aquatic contamination has been suggested as the primary cause of catastrophic otter population declines across their Eurasian range in the 1950s-1970s. Legislative controls have led to a gradual improvement in water quality, and populations are now recovering. In collaboration with the UK Environment Agency (represented by Rob Strachan), our archive of liver samples is screened for a range of contaminants (e.g. PCBs, organochlorine pesticides), and used to model spatial and temporal variation in contaminant sources, dispersal and bioavailability. Screening for inorganic elements is conducted in collaboration with the Predatory Bird Monitoring Scheme (Richard Shore & Lee Walker, based at CEH Lancaster). Recent research (with Vic Simpson, Wildlife Veterinary Investigation Centre, Cornwall) measured lead (Pb) levels in otter bone, and revealed a marked decline between 1992 and 2004, following legislative controls on Pb emissions.
2. Communication and connectivity
Otters are largely solitary, and have large home ranges (typically up to 40km of river), so direct communication between individuals is thought to be limited. It is generally assumed that otters communicate primarily using ‘spraint’, a deposit of faeces mixed with scent material from a pair of anal glands. Current research focuses on the nature of this scent signal and what is communicated (PhD student Eleanor Kean, Cardiff University), with the ultimate aim of using scent marks as a means of identifying individuals. This would provide a significant advance in otter monitoring, which is currently limited to distributional surveys (spraint indicating that ‘an otter’ has been there, but not which otter or how many).
Limitation of current monitoring methods means that information on dispersal, and hence the degree of mixing between populations, is lacking. Research using molecular genetic analysis of muscle tissues (recent PhD student Geoff Hobbs, Cardiff University) has mapped population structure within the UK, defining four populations between which there is little genetic mixing. Such research, in conjunction with analyses of habitat data, furthers our understanding of the features that influence population connectivity within and between regions.
3. Diet and nutrition
Prey availability is one of the key parameters limiting otter distribution, but studies of otter diet in much of the UK are limited both spatially and temporally. Using gut contents collected during post mortem we are able to identify prey remains, and investigate seasonal and temporal variation, as well as linking differences in diet to complementary parameters recorded at post mortem such as sex, age and size – something that most previous studies (based on prey in spraint) have not been able to achieve. Identification of prey remains from hard parts is, however, limited – some prey types can only be identified to Family level, while soft-bodied prey are not represented. Future research aims to use molecular genetic techniques to investigate diet in more detail.
Otters in Wales and England are primarily freshwater predators, but anadromous fish migrations deliver marine nutrients to freshwater catchments. In collaboration with the NERC life sciences mass spectrometry facility at East Kilbride (Rona McGill), stable isotope analysis is being used to investigate nutrient cycling, using the otter as an ‘index’ of marine nutrients and mapping their significance to freshwater food chains in Wales.
Recent and Current PhD students
Eleanor Sherrard Smith (October 2009-current) Distribution and epidemiology of macro-parasites recovered from the Eurasian Otter Lutra lutra
Eleanor Kean (April 2008-current) Otter (Lutra lutra) scent communication and development of a novel population monitoring technique.
Geoff Hobbs (2005-2009) Population genetic structure of a recovering otter (Lutra lutra) population in the UK
Recent or ongoing collaborative projects include:
UK Environment Agency – current representative on the Otter Project Board is Rob Strachan. Collaborative research focused primarily on contaminant monitoring
Richard Birtles, University of Liverpool and Dr Joanne Cable, Cardiff: tick-bourne disease
Mike Bruford, Cardiff University: otter population structure using molecular genetics
Joanne Cable, Cardiff University: endo- and ectoparasites of the otter
Dan Forman, Swansea University: wildlife as a reservoir for Toxoplasma gondii
Bill Holt, Zoological Society London and & Ian Bull, NERC LSMSF (Bristol): variation in otter scent with female reproductive status
Rona McGill, NERC LSMSF (East Kilbride): the otter as an index of marine nutrients in Wales
Carsten Müller, Cardiff University: interpretation of otter scent
Richard Shore and Lee Walker, Predatory Bird Monitoring Scheme, CEH: spatial and temporal variation in heavy metals
Vic Simpson, Wildlife Veterinary Investigation Centre: spatial and temporal variation in Pb levels
Funding for recent research has come primarily from the Environment Agency, with additional funds from RWE NPower and the Somerset Otter Group, and in kind funding from the NERC analytical facilities at both E Kilbride and Bristol.