I am studying mate choice in grey seals with a view to understanding how diversity is maintained in populations whose life history puts them at risk of inbreeding. Grey seals (Halichoerus grypus) are highly philopatric and engage in at least some level of polyandry. This means there is a risk of returning females mating with related males. Inbreeding depression in general is well documented and in grey seals heterozygosity across the genome and specifically at the MHC have been linked to surviving to adulthood. My research is creating genetic markers to investigate if this species use genome wide diversity and MHC diversity in mate choice to maximise offspring fitness.