The changes in the habitats over time have also resulted in changes to the fauna of Marjan. Consequently, species that required a large and uninterrupted habitat have disappeared in the past, however, the creation of new habitats, like grasslands or shrublands, has created the conditions which are suitable for species that otherwise could not be present in a dense forest complex, e.g., reptiles. The fauna of Marjan is isolated from the other natural areas, which can lead to the accumulation of genetic anomalies, which reduces the ability to adapt to unfavourable environmental conditions. Even though Marjan is a relatively small biological complex, many different habitats are present there. For example, many invertebrates are present on Marjan, notable among them are insects, while the rocky habitats and the grassland mosaics represent suitable habitats for various reptiles. Numerous species of birds are also present in the forest complex, while various species of bats are present in various habitats, from shrublands to grasslands. Mammals are represented by a small number of species, predominantly smaller ones. However, the fauna of Marjan requires a more thorough research and identification of species.