The Periyar protected area lies in the middle of a mountainous area of the Cardamom Hills. In the north and the east it is bounded by mountain ridges of over 1700 metres altitude and toward the west it expands into a 1200 meter high plateau. From this level the altitude drops steeply to the deepest point of the reserve, the 100 meter valley of the Pamba River. The highest peak is the 2019 meter high Kottamalai.
The sanctuary surrounds picturesque 26 km² Periyar lake, formed by the building of Mullaperiyar Dam in 1895. This reservoir and the Periyar River meander around the contours of the wooded hills, providing a permanent source of water for the local wildlife.
The temperature varies depending upon the altitude and it ranges between 15° Celsius in December and January and 31° Celsius in April and May. The annual amount of precipitation lies between 2000 and 3000 mm. About two thirds of the precipitation occurs during the southwest monsoon between June to September. A smaller amount of precipitation occurs during the northeast monsoon between October and December.
Approximately 75% of the entire protected area are covered of unaffected evergreen or semi-evergreen rain forest. There typically tall tropical tree species such as Vateria indica, Cullenia exarillata, Hopea parviflora, Canarium strictum, Artocarpus hirsutus and Bischofia javanica are seen. They reach heights of 40 to 50 Metres.
Scarcely 13% consists of damp leaves forest, 7% of Eucalyptus plantation and 1.5% of grassland. The remainder (around 3.5%) of the protected area is covered by the Periyar artificial lake as well as the Periyar River and Pamba rivers.
Altogether the reservation counts nearly 2000 kinds of flowering plants (Angiosperms), three kinds of seed plants (gymnosperms) and 170 different species of ferns. Among the Angiosperms, there are 169 families of sweet grasses and 155 kinds of Fabaceae. Orchids, with 145 representative types, are the most frequent flower.
About 350 of the occurring plant types can be used for medical purposes.
Altogether 62 different kinds of mammal have been recorded in Periyar, including many threatened ones. There are an estimated 53 tigers(2010) in the reserve. Tourists also come here to view the Indian elephants in the act of ablution and playfulness by the Periyar lake. The elephant number around 900 to 1000 individuals. Other mammals found here include gaur, sambar (horse deer), barking deer, mouse deer, Dholes (Indian wild dogs), mongoose, foxes and leopards. Also inhabiting the park, though rarely seen, are the elusive Nilgiri tahr.
Four species of primates are found at Periyar - the rare lion-tailed macaque, the Nilgiri Langur, the common langur, and the Bonnet Macaque.
So far 320 different kinds have been counted in Periyar. The bird life includes darters, cormorants, kingfishers, the great Malabar hornbill and racket-tailed Drongos.
There are 45 different kinds of reptile in the protected area out of which there are 30 snake, two turtle, and 13 lizard species. Among those are Monitor lizards that can be spotted basking in the sun on the rocks along the lake shore. Visitors who trek into the Periyar national park often see a Python and sometimes even a King Cobra.
Twenty seven different kinds have been recorded, of which ten are endemic to the Western Ghats, such as some species of frogs and cecilians.
In the waters of the protected area 38 different fish types live, of which four are endemic to the Western Ghats.Salmon,trout is also here.
There is a remarkable variety of butterflies and there are about 160 different kinds in total. Some are dangerous enough to make a human seriously ill
Major Wildlife Attractions in Periyar National Park
Periyar Wildlife Sanctuary Apart from Elephants, the other animals to be seen in the Periyar sanctuary are Gaur, Wild Pigs, Sambar, Barking Deer, Mouse Deer, Dole or Indian Wild Dog and very rarely, a Tiger. There are, now, an estimated 40 tigers here. Four species of primates are found at Periyar - the rare lion-tailed macaque, the Nilgiri Langur, Common Langur And Bonnet Macaque. Periyar also happens to be the habitat of the elusive Nilgiri Tahr, which is rarely to be seen.
The birdlife comprises of Darters, Cormorants, Kingfishers, the great Malabar Hornbill and racket-tailed Drongoes. The reptilian population boasts Of Monitor Lizards that can be spotted basking in the sun, on the rocks along the lakeshore. Visitors who trek into the Periyar national park often see a Python and sometimes even a King Cobra.