In the forests of the Neris Regional Park, one can find almost all the species of the Lithuanian forest mammals – hinds, elks, deer, boars, etc. Close to the water, beavers, building cascades of dams in torrential streams, as well as otters, minks, shrews live. All the 14 bat species existing in Lithuania are registered here. The park of Paneriai Manor and its vicinities, Dūkštos oak-wood and the settlement of Dūkštos distinguish themselves by species diversity and the abundance of bats. The „star“ of the park is the great dormouse that has been entered in the Red Data Book of Lithuania.  (Out of the 9 identified habitats in Lithuania, 3 of them are in the territory of the Neris Regional Park.) The investigations into their population have been carried out since 1999.

    


    The world of the birds of the Neris Regional Park is diverse. Here many rare birds hatch. In out-of-the-way wet woods, in old trees, the black stork – one of the bigger birds of our country – makes its nest. In spring, close to watery low wetlands, graceful cranes may be heard “trumpeting.” On forested lakesides and riversides or near old homesteads, hoopoes make nests, distinguishing from other birds by an especially big coloured crest. In the park, there are quite a few birds of prey: the most frequent bird of hawk order in our country - the buzzard, the usual ones are the sparrowhawk and the marsh harrier, quite rare and rare ones are the honey-buzzard and the hobby. The lesser-spotted eagle settles in old leafy forests. Sometimes the white-tailed eagle, the black kite, the harrier and the osprey fly in. On the escarpments of torrential streams, kingfishers burrow. At nights tawny owls hoot, in the grasslands of the Neris riverside, landrails may be often heard. In winter, in non-freezing segments of the Neris, common mergansers, common goldeneyes, mallards, swans hibernate in large flocks.

    Varied is the fish world of the Neris River. There are no dams, so ichthyofauna is formed by not only local, but also by passing fish species. Besides, there are a lot of cataracts here (the rifts of Saidė, Popai, Salinė), the Vokė, the Saidė, the Bražuolė carry their clean waters, and there is quite a big diversity of biotopes. Recently the general state of the river has obviously improved since the enterprises have reduced their activities and modern wastewater treatment facilities have been introduced. During the investigations in the segment of the river entering the territory of the park, 30 fish species were registered. Rare fish, which were found in some particular segments of the river or following specific biotopes, are the salmon, sea trout, and brown trout. Their populations are easily affected; therefore their resources need special conservation.

    

   
    During the entomology research, 1329 insect species were registered in the Neris Regional Park, 38 species out of them are new fauna in Lithuania. Frequent, widely spread insect species prevail, but rare, protected insects, and the ones, which have been entered the Lithuanian and international lists of protected species find suitable habitats and living conditions here. The Neris Regional Park distinguishes by peculiar and interesting beetle fauna with 270 registered species. Here 7 beetle species have been found, which have been entered the lists of key forest habitats. 623 moth species are found in the park. This is a little more than one forth of well-known moth species fauna in Lithuania.