Molecular scatology: The use of molecular genetic analysis to assign species, sex and individual identity to seal faeces

Seals and commercial fisheries are potential competitors for fish and cephalopods. Research into the diet of British seal species has been based on conventional dietary analyses, but these methods often do not allow assignment of species identity to seat samples. We present a protocol for obtaining DNA from seal seat (faecal) samples which can be used in polymerase chain reactions to amplify both nuclear and mitochondrial DNA. This can provide a method of identifying the species, sex and individual identity of the seal, from a particular seat sample. Combined with conventional dietary analyses these techniques will allow us to assess sources of variation in seal diet composition. Seat samples have been collected from intertidal haul-out sites around the inner Moray Firth, north-east Scotland. We have assessed methods to extract and purify faecal DNA, a combination of DNA from the individual seal, prey items, and gut bacteria, for use in PCR. Controls using faecal and blood samples from the same individual have enabled microsatellite primer sets from four pinniped species to be tested. Approximately 200 seat samples have been examined for species identity and individual matches. This study will provide essential information for the assessment of interactions between seals and commercial or recreational fisheries.