Eurasian Otter (Lutra lutra)
The Eurasian otter (Lutra lutra) is the only otter species native to the UK. They’re now present throughout the UK, having returned to many watercourses since their decline in the 1950s to 1960s. Restrictions in the UK on certain chemical pesticides and fertilisers, as well as conservation efforts have allowed for their slow recovery.
Genetic Identification of Otter from Spraints
DNA testing is particularly useful for rare, elusive or secretive wild animals such as the Eurasian otter; a largely nocturnal, secretive and semi-aquatic species. Therefore, genetic analysis of non-invasive samples (e.g. faeces) present themselves as a feasible method for obtaining genetic and population data.
Otters deposit faeces, known as spraints, on features near to water including fallen trees, logs, rocks and storm drains. Spraints are used to define and defend territories and to communicate with other otters.
Spraints are about 2-7cm long and largely contain fish bones, scales and shells. It is tarry and black and turns grey when it’s old. Having smelt spraint myself, I can confirm that it smells like jasmine tea!
Sometimes it can be difficult to distinguish between faeces of otters and other mustelid species such as minks (Mustela vison) as the stature is similar and their diets largely overlap.
We are working with local otter enthusiasts to help track, monitor and conserve County Durham’s Eurasian otter population.
We are using DNA testing technology to analyse spraints collected from the areas pinpointed on the map. We will extract DNA from the spraints for species identification, gender determination and relationship testing.
The main advantage of using DNA-based approaches is the potential to identify specimens to species level through analysis of DNA extracted from faecal samples. For otters, DNA typing of spraints can be used to provide estimates of dispersal, genetic diversity, home ranges, population size and territories for monitoring purposes.
DNA barcoding for species identification is based on a fragment of the cytochrome c oxidase subunit I (COI) gene in the mitochondrial genome. DNA barcoding technology allows for species identification by taking advantage of a DNA sequence fragment that is shared by organisms that have significant interspecies differences. This is particularly useful for when it is not possible to determine the species of an animal based on visual inspection of sample types including hair, faeces and feathers.
Otters are sexed by ZFX/ZFY sequences whereby PCR system is targeted to amplify and cut a segment of the ZFX/ZFY gene in Eurasian otter spraint samples. This assay produced one sex-specific fragment in females (XX genotypes) and two fragments in males (XY genotypes).
Identifying individuals and kinship is determined by short tandem repeat (STR) testing which compares specific loci on DNA samples that are used in relationship testing. The relationships between the otters are identified by genetic profile comparisons.