Strandzha Nature Park has the richest vertebrate fauna among all protected areas in Bulgaria — 410 species, not counting 70 species of marine fishes. There are 66 breeding mammal species. Among the most common are the roe deer, red deer, wild boar, grey wolf, golden jackal, red fox, European badger, and beech marten. The park protects some of the largest and most important populations of European otter and wildcat in Europe. The European pine marten and marbled polecat are uncommon in Strandzha. There are 25 bat species present including Bechstein's bat and Kuhl's pipistrelle. 27 species of small mammals at the park include European ground squirrel, lesser mole-rat, Günther's vole, three dormouse species, and two other globally threatened species. The park is an important sanctuary of the Roach's mouse-tailed dormouse. There have been reports on the presence of Mediterranean monk seals in the rocks and caverns of Silistar.