During the practice research period of 20 days it has been concluded that in this region live listed mamals: red fox (Vulpes vulpes), Beech marten (Martes foina), wolf (Canis lupus) and European mole (Talpa europea). There are some evidences that indicate presence of: wild boar (Sus scrofa), roe deer (Capreolus capreolus), European hare (Lepus europeus) etc.

Eventhough Orjen is orintologically attractive, there are no written data about this subject, as this region was in a turmoil of constant struggles on the border between Austro-Hungarian and Ottoman Empire. An interesting fact is that Austro-Hungarian prince Rudolf, as an ornithologist, had an interest in the research of this region. Particularly noteworthy species are: Rock partridge (Alectoris graeca), Hazel grouse (Bonasa bonasia), Golden eagle (Aquila chrysaetos), White-backed woodpecker (Dendrocropos leucotos) and Woodlark (Lullula arborea).

Facts about reptile and amphibian species are scarce. More detailed researches took place in 2008. for the needs of  a doctoral dissertation (Cirovic 2009.) In one  research in 2016.,emphasis has been given to the decription of species and habitats in order to establish real conditions, not only in the protected area but along the entire Orjen massif as well. There have been registered 20 species (15 reptile and 5 amphibion). Four of them are Balkan endemics (Yellow bellied toad, European  glass lizard, Dahl whip snake, Ursini viper) and one subendemic kind (Four lined snake). We should point up: Horned viper(Vipera ammodytes), and this species is not protected with the Resolution on protected plants and animals. IUCN category on the national level: LC (least concer /n). BEND (Balkan endemics).

Orjen is an interesting research area. Considering the invertebrate fauna, studies on ectoparasile Siphanoptera fauna, of the Balkan snow vole, were conducted in a few locations on Orjen. Pseudoscorpion is a new fauna species found on Orjen.

Species of international and national importance:

• Iphiclides podalirius Linnaeus, 1758 – Scarce swallowtail
• Papilio machaon Linnaeus 1758 – Old world swallowtail
• Parnassius apollo Linnaeus 1758 – Mountain Apollo

Orjen is a mountain without water, eventhough precipitation level reaches 5000per square metre. Water is percolating fast in the porous rocks and does not form brooks nor rivers. Only form of surface water is lokve (sth.like a big puddle). These water habitats have rich fauna, with variety of species: Leech (Hirudinae), Crustaceans (Ostracoda, Cladocera, Copepoda, Amphipoda) and insect (Odonata, Stone flies, Mayfly, Caddisfly, Fly, Beetle, True bags). Consistence and diversity of this community indicates conditions and environmental features of the ecosystem they live in. Some of aquatic invertebrates spend the first stage of their life cycle in water, and as adult forms they inhabit terrestrial ecosystems, so their presence implies that their ecosystem is wellpreserved.

Orjen is a unique mosaic of various habitats – forests,meadows,rocks and scarce aquatic habitats. These habitats are not strictly parted, but intersectioned in transitional areas, which are usually abundant in species, and a part of this abundancy are snails.

Species:

• Deroceras turcicum Simroth,1894 (air-breathing land slug)
• Limax wohlberedti (Simroth, 1900) (evenly deep black slug)
• Malacolimax mrazeki Simroth,1904 (slug dark canary- yellow)