The fauna of the Măcin Mountains, generally less studied, is diverse and has a special importance due to the presence of rare and protected species, according to international regulations.
This biodiversity paradise brings together:
-Over 1,770 plant species, of which 72 are protected as being rare or vulnerable, and 27 are endemic to the region;
-181 bird species, of which 37 are strictly protected internationally, being mentioned in the habitats directive and the Bern Convention;
-47 mammal species;
-1,436 unidentified insect species, with over 900 butterfly species;
-11 reptile species;
-7 amphibian species;
Out of the total number of birds found in the Măcin Mountains National Park (MMNP), 37 species are strictly internationally protected, as they are mentioned in the Birds directive and in the Bern Convention. For this reason the Măcin Mountains have been included in the "List if European important regions for birds". The following are nationally or world-wide rare or protected species: Lepidoptera – Polia cherrug (endemism described only in this area), the reptiles Chersotis laeta măcini and Chersotis fibriola niculescui – the Spur-thighed Tortoise (Testudo graeca ibera), four-lined snake (Elaphe quatorlineata sauromates), Aesculapian Snake (Elaphe longissima), transdanubian sand viper (Vipera ammodytes montadoni), birds - Saker Falcon (Falco cherrug), Long-legged Buzzard (Buteo ruffinus), Isabeline Wheatear (Oenanthe isabelina), existing at the Western limit of its worldwide area, Common Rock Thrush (Monticola saxatilis), European Bee-eater (Merops apiaster), Sombre Tit (Parus lugubris) etc. Regarding amphibians, according to the studies done by the Danube Delta National Institute for Research and Development (DDNIRD) through the LIFE project, the following species were found to be of great importance:
Bufo bufo (common toad) – representing a glacial relict for this area, even though being quite common in the hilly and mountainous areas of Romania, has been signaled only in 4 points in Dobrogea;
Rana dalmatina (the Agile Frog) – is spread in Dobrogea only in a limited area, in the SE neighborhood of the Măcin Mountains, being a relict which proves the antiquity of the local forests.
Regarding mammal species one can mention: red deer (Cervus elaphus), present in Dobrogea only in the Măcin Mountains, the roe deer (Capreolus capreolus), wild boar (Sus scrofa), rabbit (Lepus europaeus), fox (vulpes vulpes), wildcat (Felis silvestris), Eurasian lynx (Lynx lynx) – signaled in the Hamcearca area and with an uncertain presence in the area, marbled polecat (Vormela peregusna), beech marten (Martes foina), etc. During the last year the jackal population exploded (Canis aureus), it is the main predator of the mammals in the park.
The special importance for science and for the biodiversity of the Măcin Mountains consists in rare and endangered species: Spur-thighed Tortoise (Testudo graeca ibera) – a monument of nature, the four-lined snake (Elaphe quatorlineata), the greatest and rarest snake in Romania, the steppe polecat (Mustella eversmani), transdanubian sand viper (Vipera ammodytes montadoni), the Black Vulture (Aegypus monachus), Black Woodpecker (Dryocopus martius), and the European Roller (Coracias garrulus).
The Măcin Mountains area, according to the DDNIRD, „represents an important link on the migration routes which follow the Prut and Siret rivers. The variety of the land, forest or rocky ecosystems, combined with the presence of aquatic systems close to mountain ridges (the Jijila, Sărat, Slatina lakes, etc.), offer favorable conditions for the passing and wintering of a great number of species and specimens."