The National Park is a refuge not only for the common and well known fauna species of the Greek mountains, but also for some rare and/or endangered species. The fauna includes a great number of land-dwelling, aquatic and flying invertebrates and vertebrates, such as fish, amphibians, reptiles, birds and mammals.
The protected area is particularly important for invertebrate species, such as butterflies, grasshoppers, and beetles. 7 fish species live in the crystal water of the tributaries of the Arachthos and Acheloos Rivers, while the trout (Salmo farioides) is the predominant species living in the rivers of the area. Moreover, 10 amphibian species breed in the streams, the wet alpine fields and the seasonal ponds of the area.
The yellow-bellied toad (Bombina variegata) is found at wet locations with vegetation, the greek frog (Rana graeca) lives next to the beds of mountain streams, while toads and salamanders find shelter in the forests of the area after their breeding period. The different natural habitats of the National Park host 21 reptile species; their presence is essential for the balance of the ecosystems. The rarest reptile species found in the Lakmos and Tzoumerka mountains is the Vipera ursinii, which mainly feeds on grasshoppers.
Concerning birds, about 145 species have been recorded in the National Park. The area hosts a great number of passerine and predator birds. The presence of many predator species, as well as many large mammal species, justifies the need to institutionalise the area as a National Park. Overall, 36 predator species of the Accipitridae and Falconidae families are found here. Among them, those which stand out are: the golden eagle (Aquila chrysaetos), the griffon vulture (Gyps fulvus), the common kestrel (Falco tinnunculus), the peregrine falcon (Falco peregrinus), the lesser kestrel (Falco naumanni) etc.
7 species of woodpeckers nestle in the coniferous forests, one of which is the black woodpecker (Dryocopus martius), while the vertical slopes of Mount Lakmos and Tzoumerka Mounts are the proper habitats for many mountainous species, (e.g. Montifringilla nivalis, Alectoris graeca), which seek for their prey at the alpine and sub-alpine fields of the area.
The National Park is a particularly important area for mammals, considering that 1/4 of mammal species living in Greece have been recorded in the different habitats of the area. Especially remarkable is the presence of mammals defined as endangered species in Greece, such as the bear (Ursus arctos), the wild goat (Rupicapra rupicapra) and the otter (Lutra lutra). The presence of the wolf (Canis lupus), the roe deer (Capreolus capreolus), the wild cat (Felis sylvestris), the various bat species (in total 17) etc. denotes the diversity and the variety of the National Park’s ecosystems, highlighting the need to protect and preserve the animals and their habitats.
Concerning the livestock species present inside the National Park, it is worth mentioning the so called Boutsiko, one of the main breeds of sheep in Greece, bred by the residents of Kalarrytes and Syrrako.