The fauna is diverse with many animal species. Mammals include gray wolf, Eurasian otter, marbled polecat and numerous bat species. The avifauna includes numerous nesting species, and in addition the valley is situated on one of the most important bird migration routes in the country. Typical birds of conservation importance include Levant sparrowhawk, short-toed snake eagle, white stork, pygmy cormorant, masked shrike, lesser grey shrike, olive-tree warbler, many of them with restricted range in Southeast Europe. Sandanski–Petrich Valley is among Bulgaria's most important herpetofauna regions, including all four land and freshwater turtles species in the country, as well as most of the autochthonous snake and lizard species. The area and its surroundings are Bulgaria's only habitat of four-lined snake, and hold important populations of other range-restricted species in the country, such as European ratsnake, European cat snake, eastern Montpellier snake, Dahl's whip snake and European blind snake.
