Lough Lein (Lower Killarney Lake) lies along a natural geological fault-line between sandstone bedrock to the south-west and softer limestone around much of the eastern and southern shore. The sandstone hosts ancient Oak woodlands (e.g. at Tomies & Derrycunnihy), while a magical Yew woodland occurs on limestone bedrock at Muckross – one of the largest stands in Europe.

The juxtaposition of sandstone and limestone bedrock, along with a relatively mild climate, has resulted in an unusual and very diverse array of flora and fauna. Some of the native species found are more typically found on the Iberian Peninsula (formerly named Lusitania by the Romans) such as Strawberry Tree, St. Patrick’s Cabbage, Greater Butterwort, Irish Spurge and Kerry Slug.

Red Deer occur throughout the mountains of Kerry. It is considered that the herd in Kerry is the only truly native Irish Red Deer, as all other populations have been affected by re-introductions of Scottish Deer or have cross-hybridised with Japanese Sika Deer (which also occur in the region). During the rutting season, the stags can be heard bellowing throughout the mountains and you may well encounter jousting mature stags with interlocked antlers.

At a number of locations in the mountains, the term Eagle’s Nest can be seen. This refers Golden Eagle which formerly roamed the countryside. However, they became extinct around the turn of the 20^th century due to shooting, poisoning and egg robbing. This species has been re-introduced in Donegal and have been occasionally sighted. It is hoped that eventually these imposing birds will again breed within the Kerry Mountains.

During the summer of 2007, White-Tailed Sea Eagle was re-introduced into Killarney National Park. It is hoped that the birds will begin to breed across the wider coastal and upland regions of Kerry and West Cork. The Eagles can be seen anywhere within the Killarney Valley, but the Black Valley and Lough Léin are common foraging areas. These very large eagles lived in Ireland for thousands of years, before they were driven to extinction in the early 1900’s, due to poisoning, shooting and egg collecting.

The mountains and valleys host a myriad of pristine rivers and lakes, notably the Killarney Lakes, Lough Caragh, along with the Laune, Flesk and Caragh rivers. The Caragh River is rated one of the cleanest rivers in Europe. These support a rich and diverse aquatic fauna including Atlantic Salmon, Brown Trout, Artic Char and Killarney Shad. The latter is found only within the Killarney Lakes..

Most native Irish mammals inhabit the region, such as Otter, Pine Marten, Stoat, Bat species, Irish Hare, Red Squirrel, Badger & Fox. Sika Deer & Feral Goat are also common. Some species such as Otter and Lesser Horseshoe Bat are listed for protection under the EU Habitats Directive, while Pine Marten, Stoat and Irish Hare are endemic to this country.