Pettigo Plateau Nature Reserve is located on the western shores of Lough Derg located some 10km south east of Donegal Town. The site was designated as a Nature Reserve in 1984 to protect 900 hectares of blanket bog and wet heath. The flora includes cowberry and cranberry and a rich variety of bog mosses amongst the interlocking bog pools. The rare white sedge has also been recorded at this site. Irish hare, badger, otter and common frog are found within the site and are all listed as internationally important in the Irish Red Data Book. The Common Lizard is present within the site and can often be found basking on rocks during sunny days.
The plateau provides good hunting habitat for Merlin and Hen Harrier which can be seen at the reserve. Surrounding forestry supplies suitable nesting habitat for these species. During the spring and summer the soft mournful whistle of the Golden Plover can be heard on the higher grounds of Croaghadalough. Though uninhabited today this area was formerly part of the Leslie Estate and in the mid-1800s was occupied by two families. The remains of their small cottages and cultivation plots can still be seen in the reserve today. An old trackway runs through the reserve providing visitor access.