Though the variety of mammals to be found at Tireragan is relatively limited, the few species that do exist here are vital to the health of the ecosystem.
At several places aroung the coast both common and grey seals can be seen either curiously checking out beach walkers or hauled out on rock outcrops in sheltered bays. Otters range all along the coast crabs and fish to feed on but also cover a lot of ground on land, often creating well travelled pathways across the moorland perhaps as shortcuts between bays or to access freshwater as they frequently need to.
Just prior to the fence being completed at Tireragan all sheep and deer were driven out of the estate and even though the fence is regularly checked and maintained an occasional red deer has made its way back in and now, 15 years later, there is likely to be small numbers staying in the estate year round. The levels of regeneration have been so great that not only will a small number of deer have no significant effect on continued regeneration, low level grazing in the woodlands may well help maintain plant diversity.
The other significant grazers inside Tireragan are mountain hares and field voles which initially did cause significant damage in the areas of new planting but never had any effect on the regeneration. Interestingly, studies seem to indicate that Tireragan voles are significantly bigger than normal and this may be important for birds that prey upon them, such as kestrels, short-eared owls and hen harriers.