The fauna of Velebit is diverse and highly valuable. The area is home to populations of large carnivores (bear, wolf, and lynx) as well as other large mammals (wild boar, roe deer, red deer, and chamois). The brown bear (Ursus arctos) is the largest terrestrial carnivore in Croatia. Adult males can weigh over 300 kg, while females are significantly lighter, up to 150 kg. Shoulder height ranges from 100 to 120 cm, and when standing upright on their hind legs, bears can reach up to 2.3 m. Although classified as carnivores, bears obtain about 95% of their food from plant matter, while the remaining 5% consists mainly of animal matter, such as insects, larvae, or carrion. The brown bear is a protected species under the Nature Protection Act and the Hunting Act, but regulated hunting is permitted in accordance with the national Brown Bear Management Plan. Slightly smaller in size, the wolf (Canis lupus) belongs to the dog family; adults typically weigh around 35 kg, with a shoulder height of approximately 70 cm and a total length from snout to tail of about 170 cm. The wolf is a highly territorial species that lives in packs governed by strict hierarchical relationships. Wolves are strictly protected under the Nature Protection Act. The lynx (Lynx lynx), the third large carnivore species, belongs to the cat family. The average weight of adult males is 21 kg, while females are slightly lighter. Body length ranges from 80 to 130 cm, with shoulder height up to 60 cm. Lynx can be recognized by their short tail (15–20 cm) with a black tip, tufts of black hair on the ears, reddish-brown fur with conspicuous black spots—each individual’s pattern is unique, aiding in identification. The lynx is a territorial and solitary species, with each individual occupying its own territory. Lynx are also strictly protected under the Nature Protection Act. In addition to large carnivores, other mammal species recorded in the Park include roe deer (Capreolus capreolus), red deer (Cervus elaphus), wild boar (Sus scrofa), chamois (Rupicapra rupicapra), Eurasian otter (Lutra lutra), as well as rare and endemic species such as the Balkan snow vole (Dinaromys bogdanovi) and many others.
Bats occupy both cave and forest habitats. Mature deciduous forest stands are important foraging and roosting sites for forest-dwelling bat species, including target species such as the Barbastelle (Barbastella barbastellus) and Bechstein’s bat (Myotis bechsteinii). Caves as subterranean habitats play a crucial role in the bat life cycle, serving as maternity, hibernation, and transitional roost sites during migration. Bat species recorded in the Park’s caves include: Long-fingered bat (Myotis capaccinii), Mediterranean horseshoe bat (Rhinolophus euryale), Schreiber’s bent-winged bat (Miniopterus schreibersii), Lesser mouse-eared bat (Myotis blythii), Greater mouse-eared bat (Myotis myotis), Blasius’s horseshoe bat (Rhinolophus blasii), Geoffroy’s bat (Myotis emarginatus), Greater horseshoe bat (Rhinolophus ferrumequinum) and Lesser horseshoe bat (Rhinolophus hipposideros).
The Park’s area is exceptionally rich in birdlife, with as many as 257 species recorded. Forest habitats host a large number of cavity-nesting birds, including: Collared Flycatcher (Ficedula albicollis), Ural Owl (Strix uralensis), Boreal Owl (Aegolius funereus), Eurasian Pygmy Owl (Glaucidium passerinum) and woodpeckers such as: Black Woodpecker (Dryocopus martius), Grey-headed Woodpecker (Picus canus), Middle Spotted Woodpecker (Dendrocopos medius), White-backed Woodpecker (Dendrocopos leucotos) and very rare target species, the Three-toed Woodpecker (Picoides tridactylus). Undisturbed natural forests with a rich, mosaic habitat structure favor target species like forest grouse, including the Hazel Grouse (Bonasa bonasia) and Western Capercaillie (Tetrao urogallus). Forest habitats interspersed with clearings, meadows, small wetlands, and other open spaces are important for birds of prey, such as the target species European Honey Buzzard (Pernis apivorus).
Grassland habitats support a range of birds, including scavengers, threatened species, and those preferring ecotonal grassland edges. Dry grasslands are crucial breeding areas for the target species Rock Partridge (Alectoris graeca) and Tawny Pipit (Anthus campestris). The Corncrake (Crex crex), a priority species, inhabits floodplain and wet meadows as well as mountain grasslands. The Griffon Vulture (Gyps fulvus), both a target species and Croatia’s only vulture, was widespread in the early 20th century but now breeds regularly only on the cliffs of the Kvarner islands (Cres, Krk, Prvić, Plavnik). Short-toed Snake Eagle (Circaetus gallicus), mainly present in warm, dry areas rich in reptiles (its main prey). Red-footed Falcon (Falco vespertinus), globally endangered, recorded only twice during spring migration along the coast and southern Velebit slopes while Hen Harrier (Circus cyaneus) is a regular passage migrant and wintering bird in Croatia. Open and semi-open grasslands are also very important hunting areas for rare and endangered raptors that primarily nest on cliffs, including the critically endangered Golden Eagle (Aquila chrysaetos), Eurasian Eagle-Owl (Bubo bubo), and Peregrine Falcon (Falco peregrinus).
In the Park, two target shrike species are found: Red-backed Shrike (Lanius collurio) and Lesser Grey Shrike (Lanius minor). Both species are observed in transitional zones between grasslands and groves. These mosaic areas are also suitable for the target species Barred Warbler (Sylvia nisoria) and European Nightjar (Caprimulgus europaeus).
A total of 36 species of amphibians and reptiles have been recorded in the Park. Notable and frequently observed reptile species include: Horvath’s Rock Lizard (Iberolacerta horvathi), Four-lined Snake (Elaphe quatuorlineata), Leopard Snake (Zamenis situla) and venomous species Meadow Viper (Vipera ursinii macrops) and Nose-horned Viper (Vipera ammodytes).
The presence of saproxylic beetles, species dependent on dead wood for nutrition, such as the priority species Rosalia longicorn (Rosalia alpina), reflects the conservation, quality, and diversity of habitats. For this reason, saproxylic beetles are frequently used as ecosystem indicators. In addition to Rosalia alpina, two other target saproxylic beetle species are documented in the Park: Stag beetle (Lucanus cervus) and Morimus longicorn beetle (Morimus funereus)
Among other invertebrates, numerous species of day-flying butterflies inhabit the Park, including Apollo (Parnassius apollo) and Alcon blue (Phengaris alcon rebeli), as well as target species such as marsh fritillary (Euphydryas aurinia) and Dalmatian ringlet (Proterebia afra dalmata).
The narrow-necked cave beetle (Leptodirus hochenwartii) is the first described troglobiont invertebrate (a species strictly bound to subterranean habitats) and its discovery is considered the beginning of biospeleology. The Park area contains numerous caves and pits that host species such as: Velebit cave beetle (Velebitaphaenops giganteus), the largest known cave ground beetle of the Dinaric karst, Lika cave snail (Zospeum likanum), an endemic species of Lika and Kordun and Troglohyphantes roberti roberti (spider), an endemic of central and southern Velebit.
The Zrmanja and Ričica rivers provide suitable habitats for numerous endangered, endemic, and/or target species. Notable target fish species in the Zrmanja river include: Italian barbel (Barbus plebejus), European bullhead (Cottus gobio), Two-lined spined loach (Cobitis bilineata and Arbor dace (Alburnus arborella). The estuary of the Zrmanja is inhabited by euryhaline target species (species adapted to a wide salinity range): Panizza's goby (Knipowitschia panizzae) and Canestrini's goby (Pomatoschistus canestrinii) Lowland karst waters with reduced flow, as well as springs and associated wetlands, are home to the target species Croatian pijor (Telestes croaticus). The upper course of Zrmanja is rich in other rare (endemic) species, such as the Zrmanja chub (Squalius zrmanjae), an endemic with a very narrow range.In addition to fish, rivers and lakes of the Park host the white-clawed crayfish (Austropotamobius pallipes) and the freshwater bivalve thick-shelled river mussel (Unio crassus), an important bioindicator species.