The common or pendunculate oak (Quercus robur) is the most widespread autochthonous (native) tree of the National Park. This species, when well matured (old trees that have been growing for 100 years or more), can reach heights of up to 30 metres and support an enormous biodiversity. On the trunk and branches can be found not only fungi, lichens, mosses, and ivy (Hedera helix), but also various animal species: insects, like the stag beetle (Lucanus cervus), which lives and eats on the wood of the oak; gall wasps (small wasps that place their eggs in a plant and induce the growth of galls, inside which the larvae can develop and hatch in safety); squirrels (Sciurus vulgaris) and jays (Garrulus glandarius) which feed off acorns. There are many bird species that nest in oaks, other species that depend indirectly on the trees, whether through feeding off the insects that exist in and on oaks or from the dead leaves that fall to the ground or simply through seeking shade.