The forest area of the sanctuary is categorized into
- West Coast tropical evergreen forest,
- West Coast semi-evergreen forest and
- Southern Indian moist deciduous forest.
Fifty percent of the forests come under moist deciduous category, and 25% under semi-ever green category.
This Wild Life sanctuary is a storehouse of biodiversity.
Major mammals of the Western Ghats including elephants, bison, tiger, bear and deer are aplenty here.
All those endangered species of flora and fauna of the Western Ghats can be seen here.
A total of 110 varieties of birds including 22 types of migratory ones can be found in this sanctuary while the Chimmony water body within the sanctuary is the abode of 31 different species of local fish varieties.
Over 25 rare species of reptiles, 14 varieties of amphibians including “Churalaama” (a variety of tortoise), 100 and odd types butterflies including the world’s largest moths known as “Atlas Moth” can be seen here.
Apart from this many a rare species of endangered orchids and herbs like Mara Manjal (tree turmeric) and analivegam adds to the biodiversity of this sanctuary.
(A) Tropical Evergreen Forests
Such forests are found in the higher reaches of the Sanctuary. They are thickly wooded with lofty trees and have a closed canopy. High humidity and shade provide ideal habitats for variety of epiphytes and flowering plants. Canes and reeds are abundant. The herbaceous ground flora normally consists of species like Strobilanthus, arrowroot, ferns etc. The trees are tall, cylindrical and some with buttresses.
Top canopy is dominated by the species like Palaquim ellipticum (Pali), Mesua ferrea (Nangue), Cullenia exorillata (Vediplavu), Dipterocarpus indicus (Kalpine), Hopea parviflora (Kambakam) and Dysoxylum malabaricum (Vellagil).
Predominant species found in the lower canopy are Aporosa lindleyana (Vetti), Canarium strictum (Thelly), Euodia roxburghiana (Nasagam) and Mallotus philippensis (Karukutty)
Mainly comprises of Calamus rotang, Calamus travancoricus, Laportea crenulata and Ochlandra wightii. The ground vegetation is mostly of Wild arrowroot, Curcuma spp., Strobilanthus sp. and Ellettaria cardamomum.
(B) Semi-Evergreen Forests
These forests appear where the moist deciduous forests merge with the evergreen forests. They contain elements of both the evergreen and moist deciduous forests, the ground floor receives more light than in evergreen forests.
The dominant species in the top canopy are Adina cordifolia (Manjakadambu), Bombax ceiba (Elavu), Cedrala toona (Chandana vembu), Syzygium cumini (Njaval) and Lagerstroemia lanceolata (Venteak). Whereas the lower canopy consists of Cinnamomum zeylanicum (Edana), Evodia roxburgia (Nasagam), and Mallotus philippensis (Karukutty). Species like Calamus rotang, Calamus travencoricus, Laportea crenulata, Ochlandra wightii, Croton malabarica and Clerodendrum infortunatum constitute under growth and ground vegetation.
(C) Moist deciduous forests
These forests occur in the lower elevation of the Sanctuary. The canopy remains leafless from March to May. Adina cordifolia (Manjakadambu), Albizzia procera (Karimthakara), Alstonia scholaris (Ezhilam pala), Dalbergia latifolia (Rosewood), Lagerstroemia lanceolata (Venteak) and Xylia xylocarpa (Irul) are the dominant species in the top canopy. The lower canopy is predominantly occupied by species like Bridelia retusa (Kayanni), Careya arborea (Pezhu), Cassia fistula (Konna) and Dillenia pentagyna (Malampunna). The under growth and ground vegetation consists of Bamboosa arundinacea, Clerodendrum infortunatum, Glycosmis pentaphylla, Helicteres isora, Hollarena antidysentrica, Lantana camara, Acacia indica, Bauhunia vahlii and Calicopteris floribunda.
The following endangered species namely Alsophila spp, Lasinthus versulosus, Angioptera spp, and Gnetum ula are recorded from the sanctuary
The rare species found are
Trees : Apodytes koddemei, Diospysus nilgirica,
Shrubs : Antisroplie serratifolia, Ruwolfia densiflora
Herbs : Hydrophylla erecta, Departrium punceum
Orchids : Habomaria rariflora,Osmunda raogans