Reptiles and Amphibians make up an estimated 56 different species within Montenegro. Many of these are sub species of more common fauna such as the Green Frog and the Crested Newt. Some amphibians endemic to Montenegro have been known to undergo neoteny, such as the Olm, a small amphibian existing within mountain cave systems of the Dinaric Alps. Caves and sinkholes are common within the region resulting in a variety of endemic fauna designed live in these conditions. Around Lovćen exist common amphibians such as the Italian Crested Newt, Blue Lizard and several species of viper snakes. The Durmitor National Park is home to the Musor Rock Lizard and the Sharp Snouted lizard. Both species are native to Montenegro.