The type of animals found in a given area is the function of its existing plant communities, which in turn are governed by geo-morphology of soil, climate and rainfall conditions. The MSNP provides an excellent habitat for a wide variety of mammals, butterflies, reptiles and birds. The ground is usually covered with leaf litter, which helps in maintaining a high level of soil moisture. As a result, there is good regeneration of tree seedlings and herbaceous flora producing very characteristic microclimatic conditions supporting a rich fauna. The important mammals found in the Park are elephant, gaur, wild boar, sambar, common langur, wild dog, civets and jungle cat. Malabar giant squirrel is absent in most of the areas of the park so is the grey jungle fowl. The area is an important migratory path of elephants moving from KDH in the north to Thevaram in the south. The pioneer study on Liontailed macaque by the Japanese Primatologist Sugiyama. Y (The ecology of Liontailed macaque (Macaca silenus:. A pilot study by Sugiyama. Y (1968). JBNHS 65; 283) was carried out in these forests during 1968. But now the species is locally extinct.
The butterfly, Parantica nilgiriensis (Nymphalidae) which is restricted to some of the hills of South India and which has been listed as threatened species by IUCN was recorded to be highly abundant in the area. Besides this, these forests also harbor other rare species Libythea lepita, Pantoporia ranga, Rohana parisatis, Zipoetis saitis (Nymphalidae) and Jamides alecto (Lycaenidae), which are not commonly found in other parts of the Western Ghats. Athyma nefte, Eriboea athamas, Libythea myrrha, Ypthima avanta, Ypthima ceylonica (Nymphalidae) and Colotis fausta (Pieridae) that are commonly found in sholas of Munnar are rare in the Park. Mycalesis oculus, Vanessa indica and Cyrestis thyodamas (Nymphalidae) that are dominant at higher elevations. These species are adapted to a narrower set of climatic conditions and prefer cool and wet habitats.