Hainich is full of crawling and fluttering, croaking and shrieking, chirping and buzzing. The national park is a paradise not only for large animals. An immense variety of insects, birds, small mammals and amphibians populate the ancient woodland.
This habitat is teeming with insects. And where there are lots of insects, there are also insectivores: spiders, acarines and birds, of course, e.g. all seven species of woodpecker native to Thuringia as well as treecreeper and chaffinch. Oriol and wood warbler build their nests here, common buzzard, red kite and common raven their mighty aeries. Some of the 220 species of spider living in the national park never leave their tree top habitat. Numerous endangered butterfly species like the Purple Emperor and the poplar admiral live mainly in the tree tops of natural mixed forests.
Hainich is home not only to animal species that are typical for Central European deciduous forests (e.g. deer, badger and boar), but also to rare ones such as pine marten and hazel dormouse. Caves in large beeches provide shelter and a nursery habitat for racoons.
The succession zones are today a habitat for a number of animals living in shrubs and hedges, such as red-backed shrike, great grey shrike, grasshopper warbler and meadow pipit. The rare quail can also be seen and heard here from time to time. In winter, the open areas are a good place to spot hen harrier and rough-legged buzzard.
Deadwood is by no means dead: So-called deadwood is teeming with different species of plant and animal species. Bracket fungi, too, also often live on old or ill trees with decayed wood, since they provide ideal nutrition.
The woodland of the national park with its large share deadwood is a true eldorado for around 500 species of saproxylic beetle. New findings, refindings of species thought to be extinct and the presence of species threatened by extinction prove the significance of this habitat. Many of the beetles reach a considerable size, for example the iridescent rose chafer or the capricorn beetle.
Deadwood is an essential element in the forest's cycle. In parts of the national park, considerable stocks of deadwood have accrued already, similar to genuine primeval forests.
The shell lime soils of the national park can only hold small amounts of water. And yet it is enough to provide suitable living conditions for 13 amphibian species. There are large occurrences of tree frog, crested newt and the only 5 cm long yellow-bellied toad, who loves puddles and the water-filled tracks that are relicts from the military past.
With a little patients, dragonflies can be found around the small water-bodies in the national park (Hünenteich, Naturpfad Thiemsburg). So far (2017), 39 have been identified to live here.